Mutations In LRP5 Research Articles

Case report: exome sequencing identified mutations in the LRP5 and LGR4 genes in a case of osteoporosis with recurrent fractures and extraskeletal manifestations

BackgroundGenetic mutations have been reported in a number of bone disorders with or without extra-skeletal manifestations. The purpose of the present study was to investigate the genetic cause in a middle-aged woman with osteoporosis, recurrent fractures and extraskeletal manifestations.MethodsA 56-year-old Indian woman presented to the clinic with complaints of difficulty in walking, recurrent fractures, limb bending, progressive skeletal deformities, and poor overall health. At the age of 37, she had experienced severe anemia with diarrhea, significant weight loss, knuckle pigmentation, and a significant loss of scalp hair. She had received multiple blood transfusions and parenteral iron supplementation with normalization of hemoglobin. Subsequently, she had premature menopause at the age of 37. She died at the age of 61 due to liver failure. Exome sequencing followed by Sanger sequencing were undertaken to identify the potential pathogenic mutations.ResultsGenetic investigation identified likely pathogenic mutations in the LRP5 and LGR4 genes. Out of the two mutations, the heterozygous mutation (c.1199C>T) in the LRP5 gene resulted in a non-synonymous substitution of alanine with valine at the 400th position, and the second mutation (c.1403A>C) in the LGR4 gene led to a non-synonymous substitution of tyrosine with serine at the 468th residue of the protein. The minor allele frequencies of the c.1199C>T (LRP5) substitution in the 1000 genomes and IndiGenomes databases are 0.0003 and 0.001, while the c.1403A>C (LGR4) substitution has not been reported in these databases. Various in silico prediction tools suggested LGR4 mutation to be pathogenic and LRP5 mutation to be likely pathogenic.ConclusionHeterozygous mutations in the LRP5 and LGR4 genes had additive deteriorative effects on BMD, resulting in recurrent fractures and bone deformities, and extended the effect to extraskeletal sites, contributing to the poor overall health in this patient.

Pre-term Familial Exudative Vitreoretinopathy: A Novel Nonsense LRP5 Mutation.

This case report details the diagnosis and management of a pre-term infant with aggressive bilateral retinal pathology. A 4-week-old preterm baby girl, born at 28 weeks and 6 days to consanguineous parents, was referred for suspected aggressive posterior retinopathy of prematurity (ROP). She had a family history of bilateral retinal detachments and intellectual disability in an older sister. Clinical assessment included retinal examination, fluorescein angiography, optical coherence tomography, dual-energy X-ray absorptiometry (DEXA), and genetic testing. The genetic testing involved sequence analysis and copy number variation analysis of 25 genes related to vitreoretinopathy. Retinal examination and fluorescein angiography revealed extensive non-perfusion and telangiectatic vessels in both eyes, and a macula-involving tractional retinal detachment in the left eye. Despite treatment with intravitreal bevacizumab and laser photocoagulation, they progressed to total retinal detachment and no light perception in both eyes. Genetic testing revealed a pathogenic homozygous nonsense mutation in the LRP5 gene (c.3259C>T, p.(Gln1087*)), a mutation not previously reported in association with familial exudative vitreoretinopathy (FEVR). At 10 months of age, DEXA demonstrated normal bone density, diverging from the typical presentation of osteoporosis pseudoglioma syndrome associated with LRP5 mutations. This case describes a novel mutation in a complex retinal disease and underscores the necessity of considering pre-term FEVR in the differential diagnosis of atypical or aggressive ROP in preterm infants. The overlap in clinical features between ROP and FEVR highlights the complexity of diagnosis and management and the importance of genetic testing in preterm infants with retinal vascular abnormalities.

Idiopathic juvenile osteoporosis-a polygenic disorder?

Idiopathic juvenile osteoporosis (IJO) is a rare condition presenting with vertebral and metaphyseal fractures that affects otherwise healthy prepubertal children. Bone mineral density (BMD) measurements are very low. The primary problem appears to be deficient bone formation, with a failure to accrue bone normally during growth. The onset in childhood suggests IJO is a genetic disorder, and a number of reports indicate that some children carry heterozygous pathogenic variants in genes known to be associated with defective osteoblast function and low bone mass, most commonly LRP5 or PLS3. However, a positive family history is unusual in IJO, suggesting the genetic background can be complex. We describe a young man with classical IJO who was investigated with a bone fragility gene panel and whole genome sequencing. The proband was found to carry four variants in three different genes potentially affecting osteoblast function. From his mother he had inherited mutations in ALPL (p.Asn417Ser) and LRP5 (p.Arg1036Gln), and from his father mutations in LRP5 (p.Asp1551Alsfs*13) and activating transcription factor 4 (ATF4) (p.Leu306Ile). His sister had also inherited the LRP5 (p.Asp1551Alsfs*13) from her father, but not the ATF4 mutation. Their spinal BMD z-scores differed substantially (sister -1.6, father -3.2) pointing to the potential importance of the ATF4 mutation. Activating transcription factor 4 acts downstream from RUNX2 and osterix and plays an important role in osteoblast differentiation and function. This case, together with others recently published, supports the view that IJO can result from clustering of mutations in genes related to osteoblast development and function. Novel genes in these pathways may be involved. Our case also emphasizes the value of detailed study of other family members. After a bone biopsy had excluded a mineralization defect due to hypophosphatasia, the proband was treated with zoledronate infusions with good clinical effect.

Genetic Characteristics and Clinical Manifestations of Foveal Hypoplasia in Familial Exudative Vitreoretinopathy

This study aimed to ascertain the occurrence of foveal hypoplasia (FH) in individuals diagnosed with familial exudative vitreoretinopathy (FEVR). Retrospective cohort study. In this study, FEVR families and sporadic cases were diagnosed at the Eye and ENT Hospital, Fudan University, between 2017 and 2023. All patients attended routine ophthalmologic examinations and genetic screenings. The classification of FH was determined using optical coherence tomography (OCT) scans. The FH condition was classified into 2 subgroups: group A (FH being limited to the inner layers) and group B (FH affecting the outer layers). A total of 102 eyes from 58 patients were suitable for analysis. Forty-nine mutations in LRP5, FZD4, NDP, TSPAN12, KIF11, CTNNB1, and ZNF408 were examined and detected, with 26 of them being novel. Forty-seven eyes (46.1%) revealed FH. The majority (53.2%) were due to the typical grade 1 FH. Patients with mutations in LRP5 and KIF11 were found to exhibit a higher prevalence of FH (P = .0088). Group B displayed the lowest visual acuity compared with group A (P = .048) and the group without FH (P < .001). The retinal arteriolar angle in group B was significantly smaller than in group A (P = .001) and those without FH (P < .001). This study offers a new diagnostic approach and expands the spectrum of FEVR mutations. LRP5 and KIF11 were found to be more susceptible to causing FH in patients with FEVR. FEVR eyes with FH exhibited both greater visual impairment and reduced retinal arteriolar angles. The assessment of foveal status in patients with FEVR should be valued.

Inhibiting WNT secretion reduces high bone mass caused by Sost loss-of-function or gain-of-function mutations in Lrp5

Proper regulation of Wnt signaling is critical for normal bone development and homeostasis. Mutations in several Wnt signaling components, which increase the activity of the pathway in the skeleton, cause high bone mass in human subjects and mouse models. Increased bone mass is often accompanied by severe headaches from increased intracranial pressure, which can lead to fatality and loss of vision or hearing due to the entrapment of cranial nerves. In addition, progressive forehead bossing and mandibular overgrowth occur in almost all subjects. Treatments that would provide symptomatic relief in these subjects are limited. Porcupine-mediated palmitoylation is necessary for Wnt secretion and binding to the frizzled receptor. Chemical inhibition of porcupine is a highly selective method of Wnt signaling inhibition. We treated three different mouse models of high bone mass caused by aberrant Wnt signaling, including homozygosity for loss-of-function in Sost, which models sclerosteosis, and two strains of mice carrying different point mutations in Lrp5 (equivalent to human G171V and A214V), at 3 months of age with porcupine inhibitors for 5–6 weeks. Treatment significantly reduced both trabecular and cortical bone mass in all three models. This demonstrates that porcupine inhibition is potentially therapeutic for symptomatic relief in subjects who suffer from these disorders and further establishes that the continued production of Wnts is necessary for sustaining high bone mass in these models.

Molecular typing and mutational characterization of rectal neuroendocrine neoplasms.

Rectal neuroendocrine neoplasms (NENs) are rare neoplasms with limited understanding of its genomic alterations and molecular typing. The paraffin-embedded tissue specimens of 38 patients with rectal NENs after surgery were subjected to whole gene sequencing (WGS), and mutation profilings were drawn to identify high-frequency mutation genes, copy-number variations (CNVs), tumor mutation burden (TMB), signal pathways, mutation signatures, DNA damage repair (DDR) genes, and molecular types. The differences of mutated genes and signaling pathways in different pathological grades and metastatic/non-metastatic groups were compared. It helped to search for potential targets. C > T and T > C transitions are the most common base substitutions in rectal NENs. DNA mismatch repair deficiency, DNA base modifications, smoking and exposure to ultraviolet light might play a role in the occurrence of rectal NENs. DAXX, KMT2C, BCL2L1, LTK, MERTK, SPEN, PKN1, FAT3, and LRP2 mutations were found in only low-grade rectal NETs, whereas APC, TP53, NF1, SOX9, and BRCA1 mutations were common in high-grade rectal NECs/MiNENs. These genes helped in distinguishing poorly-differentiated or well-differentiated rectal NENs. Alterations in P53, Wnt and TGFβ signaling pathways were more pronounced in rectal NECs and MiNENs. Alterations in Wnt, MAPK and PI3K/AKT signaling pathways promoted metastases. Rectal NENs were classified into two molecular subtypes by cluster analysis based on the mutant genes and signaling pathways combined with clinicopathological features. Patients with mutations in the LRP2, DAXX, and PKN1 gene showed a trend of well-differentiated and early-stage tumors with less metastasis (p = 0.000). This study evaluated risk factors for regional lymphatic and/or distant metastases, identified high-frequency mutated genes, mutation signatures, altered signaling pathways through NGS. Rectal NENs were divided into two molecular types. This helps to evaluate the likelihood of metastasis, formulate follow-up strategies for patients and provide a target for future research on precision treatment of rectal NENs. PARP inhibitors, MEK inhibitors, mTOR/AKT/PI3K and Wnt signaling pathway inhibitors may be effective drugs for the treatment of metastatic rectal NENs.

#3593 COEXISTENCE OF 2 (DE NOVO) MUTATIONS IN 2 DIVERSE GENES (PKD1, LRP5) IN A PATIENT WITH RENAL AND LIVER POLYCYSTIC DISEASE

Abstract Introduction In Autosomal Dominant Polycystic Kidney Disease (ADPKD) the phenotype is variable. The most common extrarenal manifestation of the disease is the presence of hepatic cysts. Parallel cysts appearance in two different organs is possibly related to the genetic injury. We present in this report the case of a patient without family history of ADPKD and 2 different mutations related to cyst formation. Case report A 53 year old woman came to our outpatient ADPKD clinic with known multiple hepatic and renal cysts, diagnosed 11 years ago. She had no family history of ADPKD, both her parents aged 89 years old, had no renal or liver cysts on recent ultrasound scans. The patient had a background of recurrent UTIs, nephrolithiasis and hypertension diagnosed at 40 years old. Currently she was found to have e-GFR 49ml/min and liver function tests within normal range. Genetic testing and Magnetic Resonance Imaging (MRI) for estimating Total Kidney Volume (TKV) and hepatic imaging were conducted. In the genetic testing with a second generation sequencing, two heterozygous mutations in two different genes were depicted. The first was found in PKD1 gene: c.1396G&amp;gt;A (p.Val466Met) and causes the amino acid valine to be replaced by methionine at position 466 of the produced protein (Polycystin 1). It is reported as a variant of uncertain clinical significance because while it has been described in the literature in individuals with ADPKD, no functional studies have been performed to confirm its pathogenetic role. The second mutation concerned the LRP5 gene: c.3586G&amp;gt;A (p.Ala1196Thr) and causes the replacement of the amino acid alanine by threonine at position 1196 of the produced protein (Low density lipoprotein Receptor-related Protein-5). It is also referred as a variant of uncertain clinical significance, and exhibits autosomal dominant inheritance also. The MRI shows a particularly high cystic load in the liver (innumerable cysts) and multiple renal cysts in the two large kidneys, in a quite atypical form (not innumerable but many large cysts). The TKV was 1842 ml (1071 ml/m) and classified her in the class 1C (or possibly 2C because of the atypical form) according to the Mayo Clinic imaging classification system for ADPKD. The estimated prediction of the End-Stage Chronic Kidney Disease (ESCKD) (as long as the disease is not atypical) was according to the Mayo Clinic formula, 11 years. Discussion In a recent publication, pathological nucleotide variants of the LRP5 gene were associated with hepatic cystogenesis. Coexistence of PKD1 and LRP5 mutations was also identified in 2 families with polycystic kidney and liver disease. The underlying pathogenetic mechanism appears to be related to the connection between Polycystin-1 (the product of PKD1 involved in the pathogenesis of ADPKD) and the Wnt signaling pathway (affected by LRP5 gene mutations and linked to hepatic cystogenesis). The coexistence of the two mutations possibly means synergistic action. Unique facts and important phenotypic characteristics in this particular patient, is the de novo simultaneous appearance of the two mutations (the parents were not genetically tested but do not have cysts in very old age), the particularly large cystic liver load (which is also observed in typical ADPKD, especially in women), the atypical renal cyst imaging and the moderate to severe renal disease (expected ESCKD at 64 years, which it is more than expected in a PKD1 mutation only, but less than in a solitary PKD2 mutation). In conclusion, genetic complexity appears to go hand in hand with phenotype diversity in ADPKD and polycystic liver disease.

LRP5 BIALLELIC MUTATIONS CAUSE A HIGHER INCIDENCE OF SEVERE PHENOTYPE COMPARED WITH LRP5 MONOALLELIC MUTATION

To analyze the clinical features of LRP5 gene mutation-related familial exudative vitreoretinopathy and explore the potential phenotype-genotype correlation on LRP5 gene. Eighty-seven familial exudative vitreoretinopathy (FEVR) families with LRP5 mutations were selected from 722 FEVR patients, which were divided into 2 groups, including 22 autosomal-recessive FEVR (ar-FEVR) families and 65 autosomal-dominant FEVR (ad-FEVR) families. Clinical and genetic data were retrospectively analyzed. The potential phenotype-genotype correlation was explored from the mutation type and inheritance pattern. No significant difference between the LRP5 null mutation subgroup and the LRP5 missense mutation subgroup was observed in the proportion of FEVR stage and the ratio of ocular involvement. Instead, a significant difference between the LRP5 ar-FEVR subgroup and the LRP5 ad-FEVR subgroup was observed in the proportion of FEVR stage and the ratio of binocularly severe phenotype. The probands with LRP5 gene recessive mutation showed a higher incidence of severe phenotype. Moreover, the ratio of binocularly severe patients in ar-FEVR was nearly 3.5 times higher than that in ad-FEVR. The severity of phenotype was more likely to be related to the synergistic effect of the variants.

Novel LRP6 Mutations Causing Non-Syndromic Oligodontia.

The process of tooth formation is a series of reciprocal interactions between the ectoderm and mesoderm, and it is believed that many genetic factors are involved in this complex process. More than a dozen genes have been identified in non-syndromic tooth agenesis; however, the genetic etiology underlying tooth agenesis is not fully understood yet. In this study, we identified two novel LRP6 mutations in two non-syndromic oligodontia families. Both probands had 16 and 17 missing teeth in their permanent dentition. Mutational analysis identified a de novo frameshift mutation by a 1-bp insertion in exon 9 (NM_002336.2: c.1870dupA, p.(Met624Asnfs*29)) and a splicing donor site mutation in intron 8 (c.1762+2T>C). An in vitro splicing assay confirmed the deletion of exon 8, and the deletion would result in a frameshift. Due to the premature termination codons introduced by the frameshift, both mutant transcripts would be degraded by nonsense-mediated mRNA decay, resulting in haploinsufficiency.

Mutations in LRP6 highlight the role of WNT signaling in oral exostoses and dental anomalies

ObjectiveThe objective of this study was to investigate molecular etiologies of oral exostoses and dental anomalies in 14 patients from eight families. MethodsOral and radiographic examinations were performed on every patient. Whole exome and Sanger sequencing were performed on DNA of the patients, the unaffected parents and unaffected siblings. LRP6 mutant proteins were modeled and analyzed. ResultsFive mutations in LRP6, including four missense (p.Glu72Lys, p.Lys82Asn, Tyr418His, and p.Ile773Val) and one nonsense mutation (p.Arg32Ter), were identified. These mutations have not been reported to be associated with dental anomalies or oral exostoses. Oral features included a variety of oral exostoses (7 of the 14 patients), root defects (6 of the 14 patients), and tooth agenesis (5 of the 14 patients). Less common dental anomalies included microdontia, tooth fusion, odontomas, and mesiodens. Analysis of the protein models of the five LRP6 mutations shed light on their likely impact on LRP6 protein structure and function. ConclusionFourteen patients with five LRP6 mutations, including two recurrent mutations and three novel ones, are reported. Our study shows for the first time that mutations in LRP6 are associated with mesiodens, fusion of teeth, odontomas, microdontia, long roots, molars with unseparated roots, and taurodontism.

An LRP6 mutation (Arg360His) associated with low bone mineral density but not cardiovascular events in a Caucasian family

SummaryWe present a family with a rare mutation of the LRP6 gene and for the first time provide evidence for its association with low bone mineral density.IntroductionThe Wnt pathway plays a critical role in bone homeostasis. Pathogenic variants of the Wnt co-receptor LRP6 have been associated with abnormal skeletal phenotypes or increased risk of cardiovascular events.Patient and methodsHere we report an index premenopausal patient and her family carrying a rare missense LRP6 pathogenic variant (rs141212743; 0.0002 frequency among Europeans). This variant has been previously associated with metabolic syndrome and atherosclerosis, in the presence of normal bone mineral density. However, the LRP6 variant was associated with low bone mineral density in this family, without evidence for association with serum lipid levels or cardiovascular events.ConclusionThus, this novel association shows that LRP6 pathogenic variants may be involved in some cases of early-onset osteoporosis, but the predominant effect, either skeletal or cardiovascular, may vary depending on the genetic background or other acquired factors.

Genotype-phenotype associations in familial exudative vitreoretinopathy: A systematic review and meta-analysis on more than 3200 individuals.

ObjectiveTo systematically review the relationship between genotypes and clinical phenotypes of Familial exudative vitreoretinopathy (FEVR) to support risk estimation and therapeutic decisions.DesignSystematic review with meta-analysis.Data sourcesThe data of our study were collected from PubMed, Embase, Web of Science, Cochrane, CBM, China National Knowledge Infrastructure (CNKI), WAN FANG and VIP databases since inception to August 2021.ResultsA total of 3257 patients from 32 studies were included according to the inclusion and exclusion criteria. Among all the cases, the mutation frequencies of LRP5, FZD4, NDP, TSPAN12, ZNF408 and KIF11 were 13.6%, 11.5%, 4.6%, 6.7%, 1.6%, and 5.7%, respectively. We found that the patients with NDP and FZD4 suffer more severe symptoms, among which 86.4% patients of NDP and 78.6% patients of FZD4 were in the advanced stage of FEVR. Retinal detachment is the most frequent symptom with patients of LRP5 and NDP mutations, accounting for 51.9% and 64.5%, respectively. For the patients with the mutation of TSPAN12, retinal fold is the most common clinical manifestation, and suffer the mildest clinical phenotypes compared with the other three genes.ConclusionThe results of the meta-analysis indicate that different types of genetic mutations occur at different frequencies. In addition, the clinical manifestations of FEVR are related to the type of gene mutation. Therefore, targeted treatment strategies and follow-up recommendations should be adopted for different pathogenic genes of FEVR.

Mutations in LRP5 and BMP4 are associated with mesiodens, tooth agenesis, root malformation, and oral exostoses.

WNT/β-catenin and BMP signaling pathways play important roles in the process of tooth development. Dysregulation of WNT/β-catenin and BMP signaling is implicated in a number of human malformations, including dental anomalies. Whole exome and Sanger sequencing identified seven patients with LRP5 mutations (p.Asn1121Asp, p.Asp856Asn, p.Val1433Met, and p.Val1245Met) and six patients with BMP4 mutations (p.Asn150Lys, p.Gly168Arg, p.Arg269Gln, and p.Ala42Glu). All patients were affected with isolated dental anomalies (dental anomalies with no other structural defects), including mesiodens, tooth agenesis, unseparated roots, narrow roots, shortened and tapered roots, and taurodontism. Five patients with LRP5 and one with BMP4 mutations had oral exostoses. Protein models of LRP5 mutations indicate the possible functional effects of the mutations. Here we report for the first time that mutations in LRP5 are associated with dental anomalies. LRP5 appears to be the first gene related to pathogenesis of mesiodens. We also show for the first time that in addition to tooth agenesis, mutations in BMP4 are also implicated in root maldevelopment and torus mandibularis. Sharing of the phenotypes of the patients with LRP5 and BMP4 mutations, which include root maldevelopment, tooth agenesis, and torus mandibularis, implicates cross talks between the WNT/β-catenin and BMP signaling pathways, especially during root development.

Commentary: Familial exudative vitreoretinopathy-The masquerade in pediatric retinal disorders.

This issue of IJO features an interventional study discussing the clinical profile, management, and outcomes of pediatric macula-off rhegmatogenous retinal detachment (RRD) secondary to familial exudative vitreoretinopathy (FEVR).[1] FEVR is a rare inherited disorder of retinal angiogenesis, characterized by phenotypic and genotypic heterogenicity.[2] Phenotypic expression may range from the presence of temporal avascular peripheral retina in an asymptomatic patient to extensive subretinal exudation, florid fibrovascular proliferation, retinal folds, tractional retinal detachment (RD) or RRD, or severe retinal dysplasia at birth resulting in severe visual dysfunction and even total blindness.[2] Treatment options include observation, laser photocoagulation or cryotherapy, anti-vascular endothelial growth factor (anti-VEGF) injection and scleral buckle, and/or pars plana vitrectomy (PPV), depending upon the stage of disease at presentation.[2] Management of RRD in FEVR is complicated by its presentation in younger age as well as by the underlying abnormal vitreoretinal interface, which is more adherent and difficult to completely separate from the retina, resulting in postoperative pre-retinal proliferation and recurrent RD.[3] Unique surgical problems are associated with these RRDs, especially in the presence of associated falciform retinal folds.[3] Where peripheral breaks with falciform folds can be supported on a scleral buckle, posterior retinal breaks in eyes with falciform folds necessitating PPV and large posterior relaxing retinectomies result in particularly dismal outcomes.[3] Due to phenotypic variability, improper and delayed diagnosis is the biggest hurdle in the management of FEVR. When presenting in the neonatal period, it can masquerade other pediatric retinal disorders like retinopathy of prematurity (ROP) and persistent fetal vasculature (PFV).[2] A small subset of premature infants who exhibit retinal findings more characteristic of FEVR than ROP have been described as ROPER (ROP vs. FEVR) by Gologorsky et al.[4] These eyes behave more like FEVR, with a less predictable and more progressive course of disease in long term.[4] FEVR can mimic PFV, especially if associated with “knifelike retinal folds “extending from the optic disk radially to the peripheral retina and anteriorly to the ciliary processes.[2] It is quite possible for a patient to have advanced FEVR findings in one eye and grossly normal other eye, further creating confusion with PFV. The stalk in PFV, unlike the falciform fold in FEVR, is not typically a retinal fold, but a hyaloid stalk of persistent vascular tissue that extends from the optic nerve to the posterior lens surface.[5] Accurate diagnosis of FEVR is best done by careful clinical examination coupled with fundus fluorescein angiography (FFA) and genetic testing wherever possible. FFA enhances the diagnostic sensitivity because subtle vascular changes in the periphery or even in the posterior pole can easily be overlooked by a routine fundus examination.[2] Wide-field retinal imaging is particularly helpful to detect asymptomatic family members. Because of phenotypic variations, genetic testing may become essential in some cases to establish the diagnosis. The inheritance pattern of FEVR may be autosomal dominant (AD; most common), autosomal recessive (AR), or X-linked recessive (XL-R), and the common genes implicated so far include NDP, FZD4, LRP5, TSPAN12, ZNF408 and KIIF11.[267] The first four genes result in mutations in the “Norrin/b-catenin signaling pathway,” which plays a pivotal role in vascular morphogenesis in the eye.[2] KIF11, localized to the spindle microtubules, is involved in the mitotic progression and growth of the retinal vessels.[6] The ZNF408 protein has been implicated in abnormal retinal vascularization and trunk vascularization in zebrafish.[7] While almost all patients with NDP mutations are reported to have a severe presentation, milder phenotypes ranging from stage 2 to stage 5 have been seen in eyes with LRP5 mutations.[8] Disease phenotype is reportedly more bilaterally symmetrical in patients with KIFF11, TSPAN12, and NDP gene mutations compared to patients with LRP5 and FZD4 mutations.[9] Widespread chorioretinal degeneration may additionally be present in cases with KIFF11 and NDP mutations, along with neurodevelopmental delay and microcephaly.[10] Genetic testing in FEVR is important for diagnosis, better understanding of the disease, and prognostication. Knowledge of the gene mutation can also facilitate the molecular prenatal analysis of fetal DNA; this along with antenatal ultrasound can be used to predict FEVR in at-risk babies.[11] Timely intervention in the early neonatal period itself can prevent total blindness in some at-risk babies. FEVR, a clinically and genetically heterogeneous disorder, requires a high index of suspicion, careful examination, timely management, and long-term follow-up. Increased genetic testing in these patients will further improve our understanding of the disease. Awareness and education of parents as well is of paramount importance to reduce the risk of bilateral total blindness due to FEVR.

Evaluation of growth, puberty, osteoporosis, and the response to long-term bisphosphonate therapy in four patients with osteoporosis-pseudoglioma syndrome.

Osteoporosis-pseudoglioma syndrome (OPPG; MIM #259770) is a rare autosomal recessively inherited disease, characterized by early-onset osteoporosis and congenital blindness, caused by loss-of-function mutations in the LRP5 gene. Beneficial effects of bisphosphonate treatment in patients with OPPG are well known, while follow-up data on growth and pubertal parameters are limited. This article provides clinical follow-up data and long-term bisphosphonate treatment results in four OPPG patients from three unrelated families, ranging between 2.5 and 7 years of age at presentation. Clinical diagnosis was molecularly confirmed in all patients, with four different germline biallelic LRP5 mutations including a novel nonsense variant c.3517C>T (p.(Gln1173*)) in two siblings with marked phenotypic variability. Anthropometric and pubertal data and bone mineral density (BMD) measurements were evaluated retrospectively. Early puberty was observed in two patients. The bisphosphonate treatment duration of patients varied around 4-7 years and improvement in BMD z-scores with bisphosphonate treatment was demonstrated in all patients (z-score changes were +5.6, +4.0, +1.0, and +1.3). Although further research is needed to identify the possible association between early puberty and OPPG, all OPPG patients should be followed up with detailed endocrinological evaluation regarding pubertal status.

Whole Exome/Genome Sequencing Joint Analysis of a Family with Oligogenic Familial Hypercholesterolemia.

Autosomal Dominant Hypercholesterolemia (ADH) is a genetic disorder caused by pathogenic variants in LDLR, APOB, PCSK9 and APOE genes. We sought to identify new candidate genes responsible for the ADH phenotype in patients without pathogenic variants in the known ADH-causing genes by focusing on a French family with affected and non-affected members who presented a high ADH polygenic risk score (wPRS). Linkage analysis, whole exome and whole genome sequencing resulted in the identification of variants p.(Pro398Ala) in CYP7A1, p.(Val1382Phe) in LRP6 and p.(Ser202His) in LDLRAP1. A total of 6 other variants were identified in 6 of 160 unrelated ADH probands: p.(Ala13Val) and p.(Aps347Asn) in CYP7A1; p.(Tyr972Cys), p.(Thr1479Ile) and p.(Ser1612Phe) in LRP6; and p.(Ser202LeufsTer19) in LDLRAP1. All six probands presented a moderate wPRS. Serum analyses of carriers of the p.(Pro398Ala) variant in CYP7A1 showed no differences in the synthesis of bile acids compared to the serums of non-carriers. Functional studies of the four LRP6 mutants in HEK293T cells resulted in contradictory results excluding a major effect of each variant alone. Within the family, none of the heterozygous for only the LDLRAP1 p.(Ser202His) variant presented ADH. Altogether, each variant individually does not result in elevated LDL-C; however, the oligogenic combination of two or three variants reveals the ADH phenotype.

Potential therapeutic response in a severe case of autosomal dominant osteopetrosis type I

The low-density lipoprotein receptor-related protein 5 gene (LRP5), which encodes a coreceptor within the canonical Wnt signaling pathway, plays a crucial role in bone mass regulation and has been associated with several bone disorders. Autosomal dominant osteopetrosis type I (ADO type I, OMIM 607634) is a rare disease caused by heterozygous, gain-of-function mutations in LRP5. Here we describe a 44-year-old female who presented with thickened calvarium, elevated bone density, torus palatinus, mandibular exostoses, enlarged mandible, and disabling headaches and bone pain. Exome sequencing revealed a previously reported heterozygous missense variant in the LRP5 gene (p.A242T). Post-diagnosis cranial vault volume measurement by computed tomography 3D reconstruction demonstrated decreasing intracranial volume over time. Off-label use of leuprolide acetate was associated with apparent stabilization of skull mineralization. This report documents a severe example of ADO type I and provides anecdotal evidence of the utility of therapy in need of formal evaluation.

Ocular Features and Mutation Spectrum of Patients With Familial Exudative Vitreoretinopathy.

PurposeTo investigate the clinical findings in Chinese patients diagnosed with familial exudative vitreoretinopathy (FEVR) and carrying pathogenic mutations.MethodsOne hundred twenty unrelated patients with FEVR were enrolled in this study. Genomic DNA and ophthalmic examinations were collected from all the patients and their available relatives. Targeted next-generation sequencing was performed to detect mutations. In silico programs were used to evaluate the pathogenicity of all the mutations.ResultsEighty identified mutations were found in 81 unrelated patients (31/81 in LRP5, 25/81 in FZD4, 12/81 in TSPAN12, 8/81 in NDP, 4/81 in KIF11, and 1/81 in ZNF408). Among those mutations, 53 were novel (23/35 in LRP5, 15/21 in FZD4, 8/11 in TSPAN12, 3/8 in NDP, 3/4 in KIF11, 1/1 in ZNF408). Patients with LRP5, FZD4, TSPAN12, or NDP mutations were mainly classified into stage 4 and stage 5 and one-half of patients with KIF11 mutations were in stage 4. In addition, all the patients in NDP group were found to have bilateral symmetry in FEVR stage.ConclusionsOur results present profound phenotypic variability and a wide mutation spectrum of FEVR in the Chinese population, which could be useful for a precise and comprehensive genetic diagnosis for patients with FEVR in the future.

Expanding the phenotypic spectrum of mutations in LRP2: a novel candidate gene of non-syndromic familial comitant strabismus

BackgroundComitant strabismus (CS) is a heterogeneous disorder that is a major contributing factor to unilateral childhood-onset visual impairment. Studies have confirmed that genetic factors play an important role in the development of CS. The aim of this study was to identify the genetic cause of non-syndromic familial CS.MethodsFourteen unrelated CS families were recruited for the study. Twelve affected and 2 unaffected individuals from a large four-generation family (CS08) were selected to perform whole genome-wide linkage analysis. Parallel whole-exome sequencing (WES) was conducted in the same family (9 patients and 1 unaffected member) and 31 additional CS cases from 13 other unrelated families. Sanger sequencing was used to determine whether any of the remaining variants co-segregated with the disease phenotype in the corresponding family.ResultsBased on linkage analysis, CS in family CS08 mapped to a novel region of 34.17 centimorgan (cM) on chromosome 2q22.3-2q32.1 between markers D2S151 and D2S364, with a maximum log odds (LOD) score of 3.54 (theta = 0) at D2S142. Parallel WES identified a heterozygous variant, LRP2 c.335 A > G (p.Q112R), located in such a linkage interval that completely co-segregated with the disease in the family. Furthermore, another novel heterozygous variant (c.7274A > G, p.D2425G) in LRP2 that co-segregated was detected in 2 additional affected individuals from another unrelated family by WES. Both variants are predicted to be damaging by PolyPhen-2, SIFT and MutationTaster, and were absent in 100 ethnically matched normal controls.ConclusionLRP2 is a novel candidate genetic cause of non-syndromic familial CS.

Activation of canonical Wnt signaling accelerates intramembranous bone regeneration in male mice.

Canonical Wnt signaling plays an important role in skeletal development, homeostasis, and both endochondral and intramembranous repair. While studies have demonstrated that the inhibition of Wnt signaling impairs intramembranous bone regeneration, how its activation affects intramembranous bone regeneration has been underexplored. Therefore, we sought to determine the effects of activation of canonical Wnt signaling on intramembranous bone regeneration by using the well-established marrow ablation model. We hypothesized that mice with a mutation in the Wnt ligand coreceptor gene Lrp5 would have accelerated intramembranous bone regeneration. Male and female wild-type and Lrp5-mutant mice underwent unilateral femoral bone marrow ablation surgery in the right femur at 4 weeks of age. Both the left intact and right operated femurs were assessed at Days 3, 5, 7, 10, and 14. The intact femur of Lrp5 mutant mice of both sexes had higher bone mass than wild-type littermates, although to a greater degree in males than females. Overall, the regenerated bone volume in Lrp5 mutant male mice was 1.8-fold higher than that of littermate controls, whereas no changes were observed between female Lrp5 mutant and littermate control mice. In addition, the rate of intramembranous bone regeneration (from Day 3 to Day 7) was higher in Lrp5 mutant male mice compared to their same-sex littermate controls with no difference in the females. Thus, activation of canonical Wnt signaling increases bone mass in intact bones of both sexes, but accelerates intramembranous bone regeneration following an injury challenge only in male mice.