COL7A1 Mutations Research Articles

Novel variants impairing Sp1 transcription factor binding in the COL7A1 promoter cause mild cases of recessive dystrophic epidermolysis bullosa.

Recessive dystrophic epidermolysis bullosa (RDEB) is a rare and most often severe genodermatosis characterized by recurrent blistering and erosions of the skin and mucous membranes after minor trauma, leading to major local and systemic complications. RDEB is caused by loss-of-function mutations in COL7A1 encoding type VII collagen (C7), the main component of anchoring fibrils which form attachment structures stabilizing the cutaneous basement membrane zone. Most of the previously reported COL7A1 mutations are located in the coding or intronic regions. We describe 6 patients with localized or intermediate RDEB for whom one recessive pathogenic variant in the coding region and a second variant in the COL7A1 promoter were identified. These substitutions, three of which are novel, are localized in two Sp1 binding sites of the promoter region. DNA pull-down assay showed a drastic reduction of Sp1 binding consistent with a dramatic decrease in COL7A1 transcript and almost undetectable C7 protein levels. Our results reveal that mutations in the COL7A1 promoter on the background of a null allele can underlie localized or intermediate RDEB. They further emphasize the functional importance of Sp1 motifs in the proximal COL7A1 promoter which should be carefully investigated for regulatory mutations in the case of RDEB with only one pathogenic variant identified in the coding or intronic regions.

Lung function in adult patients with osteogenesis imperfecta: a cohort study

BackgroundOsteogenesis imperfecta (OI) is a rare hereditary bone disease resulting from a defect in collagen synthesis or processing, leading to bone fragility, frequent fractures and skeletal deformities. OI is associated with increased respiratory morbidity and mortality, but the mechanisms of lung involvement are poorly understood, and there are no data on the natural history of lung function. We studied lung function over time in a cohort of adult OI patients at one center.MethodsWe used data from OI patients aged 15 and above followed up at the Lausanne university hospital between 2012 and 2023 with available pre-bronchodilator spirometry. Associations between spirometric measurements at first visit and clinical characteristics were studied through linear regression. Changes of spirometric variables over time were analysed through mixed linear regression. Models were adjusted for age, sex, height and OI type (Sillence classification).ResultsAmong 46 subjects, 24% had impaired spirometry at baseline, with similar distribution between restrictive (8.7%), obstructive (8.7%) and mixed (6.5%) ventilatory patterns. At first visit, higher age was associated with lower FEV1 (β = −0.019 l, p = 0.014) and lower FEV1/FVC (β = −0.175%, p = 0.012). A history of asthma was associated with higher FEV1 (β = 0.636 l, p = 0.028) and FVC (β = 0.834 l, p = 0.010). At first visit, FEV1 (β = −0.750 l, p = 0.006) and FVC (β = −0.859 l, p = 0.004) was lower in individuals with OI Sillence types 3, 4 or 5 compared to type 1. Over a mean follow-up of 3.4 years, smokers had a greater decline of FEV1/FVC compared to non-smokers (β = −6.592%, p = 0.007). Individuals with a mutation in the gene COL1A2 had 740 ml lower FVC compared to those with a mutation in COL1A1 (p = 0.037). After adjustment for sex, age, height and OI type, FEV1 increased by 26 ml (95% CI 8; 45) or 1.28%pred (0.51; 2.05) and FVC increased by 25 ml (95% CI 8; 43) or 0.93%pred (0.31; 1.55) per year of follow-up.ConclusionsAn increase of FEV1 and FVC over time was observed in OI patients after adjustment for other variables, suggesting that the defective collagen synthesis may impact the pulmonary interstitium and lead to increased lung compliance and hyperinflation, in contrast to skeletal deformities, which reduce the thoracic volume. Lung function changes in OI thus result from the interplay of several mechanisms.

Integrative Multi-Omics Approach in Vascular Ehlers–Danlos Syndrome: Further Insights into the Disease Mechanisms by Proteomic Analysis of Patient Dermal Fibroblasts

Background: Dominant mutations in COL3A1 are known to cause vascular Ehlers–Danlos syndrome (vEDS) by impairing extracellular matrix (ECM) homeostasis. This disruption leads to the fragility of soft connective tissues and a significantly increased risk of life-threatening arterial and organ ruptures. Currently, treatments for vEDS are primarily symptomatic, largely due to a limited understanding of its underlying pathobiology and molecular mechanisms. Methods: In this study, we conducted a comprehensive analysis of the intracellular proteome of vEDS fibroblasts, integrating these findings with our previous transcriptome results to identify key molecular pathways that drive the disease. Additionally, we explored the therapeutic potential of inhibiting miR-29b-3p as a proof of concept. Results: Our integrative multi-omics analysis revealed complex pathological networks, emphasizing the critical role of miRNAs, particularly miR-29b-3p, in impairing ECM organization, autophagy, and cellular stress responses, all of which contribute to the pathogenesis of vEDS. Notably, the inhibition of miR-29b-3p in vEDS fibroblasts resulted in the upregulation of several differentially expressed target genes involved in these critical processes, as well as increased protein expression of essential ECM components, such as collagen types V and I. These changes suggest potential therapeutic benefits aimed at improving ECM integrity and restoring intracellular homeostasis. Conclusions: Overall, our findings advance our understanding of the complex biological mechanisms driving vEDS and lay a solid foundation for future research focused on developing targeted and effective treatment strategies for this life-threatening disorder.

Rhegmatogenous Retinal Detachment Secondary to Type I Stickler Syndrome: Diagnosis, Treatment and Long-Term Outcomes.

This study aimed to clarify the genetic diagnosis of rhegmatogenous retinal detachment (RRD) secondary to type I Stickler syndrome (STL1) and evaluate the anatomical and functional outcomes of surgical treatment. This retrospective study included 11 patients with RRD secondary to STL1. Familial and sporadic cases of STL1 were diagnosed at the Eye & ENT Hospital, Fudan University, between 2017 and 2023. To clarify the genetic diagnosis, next-generation sequencing was performed in suspected STL1 cases. Further, standard ocular examinations and surgical treatment were performed. Nine variants of COL2A1, including four novel mutations (c.394G>T, c.2977G>T, c.3003+2dup, and c.3853G>C), were screened and identified. The pathogenicity of all variants was conclusively demonstrated. Among patients who underwent vitrectomy, the mean age at RRD was 11.5 years, and the mean follow-up was 32.9 months. The average number of surgical procedures required during the follow-up was two; 90.9% of eyes achieved final attachment, and best corrected visual acuity (BCVA) significantly improved in 81.8% of the eyes, with a middle postoperative logMAR BCVA of 0.52 compared with the preoperative value (p = 0.0148). High intraocular pressure (81.8%) and cataract (72.7%) were the most common complications. Our study expands the spectrum of COL2A1 mutations and provides a novel diagnostic strategy for STL1. By combining clinical manifestations with genetic testing, STL1 could be accurately diagnosed. With proper surgical treatment and long-term follow-up, the prognosis of RRD in patients with STL1 could be improved.

Analysis of a Familial IgAN Accompanied by COL4A3 Mutation.

IgA nephropathy (IgAN) is the prevailing primary glomerulonephritis globally and is the key factor contributing to the onset of chronic kidney disease and eventual progression to end-stage renal disease. This study aims to explore the mutated gene in a familial case of IgAN, especially COL4A3. Family lineages diagnosed with familial IgAN at the Longyan First Hospital of Fujian Medical University were selected for this study, followed by comprehensive whole exome sequencing. After obtaining the sequencing data, bioinformatics analyses were conducted to discern potential mutated genes. These findings within the familial lineages were validated using Sanger sequencing to identify IgAN-associated mutated genes, based on literature references and in accordance with the genetic variation classification criteria determined by the American College of Medical Genetics and Genomics. Whole exome sequencing analysis of familial IgAN family lineages led to the identification of a total of 212,187 single nucleotide variant/insertion-deletion mutation sites, annotated using ANNOVAR. These sites were screened targeting four mutated genes, revealing three mutations of undetermined significance along with a single disease-causing mutation: a heterozygous disease-causing mutation within COL4A3 (p.G1167R). This mutation manifested across seven family members within the group, encompassing both family members diagnosed with kidney disease and those serving as normal carriers. Notably, one additional family member with IgAN within the familial lineage exhibited an absence of the pathogenic mutation. This study identified four mutated genes that may be involved in the onset and progression of IgAN, further revealing the complex multigenic inheritance characteristics of IgAN. The underlying mechanisms of the disease require further investigation. Additionally, we discovered potential mutations associated with known genetic kidney diseases, such as COL4A3 mutations. Therefore, we recommend comprehensive genetic screening in familial cases of IgAN to improve disease diagnosis and facilitate genetic counseling.

Osteoclast indices in osteogenesis imperfecta: systematic review and meta-analysis.

Osteogenesis imperfecta (OI) is a rare bone fragility disorder caused by mutations in genes encoding collagen type I or that affect its processing. Alterations in osteoclasts were suggested to contribute to OI pathophysiology. We aimed to systematically identify studies reporting measures of osteoclast formation and function in patients and mouse models of OI, to quantify OI-induced changes. The systematic search of Medline, Ovid, and Web of Science identified 798 unique studies. After screening, we included 23 studies for meta-analysis, reporting osteoclast parameters in 310 patients with OI of 9 different types and 16 studies reporting osteoclast parameters in 406 animals of 11 different OI mouse models. The standardized mean difference with 95% confidence interval (CI) was used as the effect size, and random-effects meta-analysis was performed. In patients with OI, collagen degradation markers were significantly higher compared with age-matched controls, with an effect size of 1.23 (CI: 0.36, 2.10]. Collagen degradation markers were the most elevated in the 3- to 7-year-old age group and in patients with more severe forms of OI. Bone histomorphometry demonstrated the trends for higher osteoclast numbers (1.16; CI: -0.22, 2.55) and osteoclast surface (0.43; CI: -0.63, 1.49), and significantly higher eroded surface (3.24; CI: 0.51, 5.96) compared with age-matched controls. In OI mice, meta-analysis demonstrated significant increases in collagen degradation markers (1.59; CI: 1.07, 2.11), in osteoclast numbers (0.94; CI: 0.50, 1.39), osteoclast surface (0.73; CI: 0.22, 1.23), and eroded surface (1.31; CI: 0.54, 2.08). The largest differences were in OI mice with the mutations in Col1a1 and Col1a2 genes. There were no differences between males and females in clinical or animal studies. Quantitative estimates of changes in osteoclast indices and their variance for patients with OI are important for planning future studies. We confirmed that similar changes are observed in mice with OI, supporting their translational utility.

Heterozygous COL11A1 mutation associated with congenital cataract, lens subluxation, and zonular loss

Heterozygous COL11A1 mutation associated with congenital cataract, lens subluxation, and zonular loss

Distinct muscle regenerative capacity of human induced pluripotent stem cell-derived mesenchymal stromal cells in Ullrich congenital muscular dystrophy model mice

BackgroundUllrich congenital muscular dystrophy (UCMD) is caused by a deficiency in type 6 collagen (COL6) due to mutations in COL6A1, COL6A2, or COL6A3. COL6 deficiency alters the extracellular matrix structure and biomechanical properties, leading to mitochondrial defects and impaired muscle regeneration. Therefore, mesenchymal stromal cells (MSCs) that secrete COL6 have attracted attention as potential therapeutic targets. Various tissue-derived MSCs exert therapeutic effects in various diseases. However, no reports have compared the effects of MSCs of different origins on UCMD pathology.MethodsTo evaluate which MSC population has the highest therapeutic efficacy for UCMD, in vivo (transplantation of MSCs to Col6a1-KO/NSG mice) and in vitro experiments (muscle stem cell [MuSCs] co-culture with MSCs) were conducted using adipose tissue-derived MSCs, bone marrow-derived MSCs, and xeno-free-induced iPSC-derived MSCs (XF-iMSCs).ResultsIn transplantation experiments on Col6a1-KO/NSG mice, the group transplanted with XF-iMSCs showed significantly enhanced muscle fiber regeneration compared to the other groups 1 week after transplantation. At 12 weeks after transplantation, only the XF-iMSCs transplantation group showed a significantly larger muscle fiber diameter than the other groups without inducing fibrosis, which was observed in the other transplantation groups. Similarly, in co-culture experiments, XF-iMSCs were found to more effectively promote the fusion and differentiation of MuSCs derived from Col6a1-KO/NSG mice than the other primary MSCs investigated in this study. Additionally, in vitro knockdown and supplementation experiments suggested that the IGF2 secreted by XF-iMSCs promoted MuSC differentiation.ConclusionXF-iMSCs are promising candidates for promoting muscle regeneration while avoiding fibrosis, offering a safer and more effective therapeutic approach for UCMD than other potential therapies.

Hemoperitoneum Due to Dissection and Rupture of the Superior Mesenteric Artery in a Patient With COL3A1 Mutation.

Introduction: Vascular Ehlers-Danlos syndrome (vEDS) is an autosomal dominant disorder that results from mutations in the collagen type III gene. It is a risk factor for medium-sized artery aneurysms, dissections, and ruptures. We report a case of hemoperitoneum due to medial dissection and rupture of the superior mesenteric artery related to vEDS. Methods: A full body CT scan and full three cavity autopsy was performed in a 47-year-old man with a history of an intermittent abdominal cramping for one week rand complex past medical history that included a sigmoid bowel perforation at age 20, and previous popliteal artery pseudoaneurysm rupture. Histology and genetic testing were performed. Results: The postmortem computed tomography and autopsy showed a significant hemoperitoneum due to a ruptured dissection of the superior mesenteric artery and branches, and multiple splanchnic artery dissections with renal and small bowel infarctions. Genetic testing revealed a heterozygous COL3A1 gene variant associated with Ehlers-Danlos syndrome. Death was attributed to hemoperitoneum due to medial dissection and rupture of the superior mesenteric artery due to arteriopathy. Discussion: The relatively young age and medical history correlate with the autopsy findings and genetic testing towards the conclusion of an arteriopathy consistent with vEDS.

A comprehensive review of Alport syndrome: definition, pathophysiology, clinical manifestations, and diagnostic considerations.

Alport syndrome, a rare genetic disorder affecting around 1 in 50,000 individuals, primarily presents as microscopic hematuria and chronic kidney disease (CKD) with associated extrarenal complications. The Alport syndrome results from mutations in COL4A3, COL4A4, and COL4A5 genes, disrupting the formation of the α3-α4-α5 chain in the collagen IV network. The etiology involves X chromosome-related, autosomal dominant, autosomal recessive, and digenic inheritance patterns. The disease primarily manifests as kidney involvement, featuring persistent hematuria, proteinuria, and a progressive decline in renal function. Hearing loss, ocular abnormalities, and extrarenal manifestations further contribute to its complexity. Genotype-phenotype correlations are relatively evident, with distinct presentations in X-linked, autosomal recessive, and autosomal dominant cases. Diagnosis relies on urinalysis, histologic examination, and genetic testing with advancements in next-generation sequencing aiding identification. Although no specific treatment exists, early diagnosis improves outcomes, emphasizing the importance of genetic testing for prognosis and familial screening. The purpose of this review is to advance knowledge and enhance understanding of Alport syndrome.

A homozygous nonsense mutation identified in COL7A1 in a family with autosomal recessive dystrophic epidermolysis bullosa.

Autosomal recessive dystrophic epidermolysis bullosa (RDEB) is a severe form of an inherited skin disorder. RDEB segregates both in an autosomal dominant as well as in an autosomal recessive pattern. It has been shown that both forms of dystrophic epidermolysis bullosa (DEB) are caused by mutations in the COL7A1 gene. In this study, we investigated a consanguineous four-generation family with two individuals displaying the RDEB phenotype. Both patients showed multiple skin erosions, atrophic scares, crusted scaling, and pseudosyndactyly. Whole exome sequencing (WES) was performed to identify the underlying genetic defect, revealing a homozygous nonsense mutation, c.409C>T (p.Arg137*) in COL7A1 in both patients. This variant was validated through Sanger sequencing and confirmed to segregate within the family. This report describes a recurrent nonsense mutation in COL7A1 that leads to a severe form of autosomal recessive dystrophic epidermolysis bullosa. Moreover, this study demonstrates that whole exome sequencing analysis is imperative in resolving clinically and genetically heterogeneous diseases like RDEB. Furthermore, this study expands the mutation spectrum of the COL7A1 gene in distinct populations.

Chemical chaperones to the rescue of Alport syndrome?

Alport syndrome is a hereditary kidney disease caused by collagen IV mutations that interfere with the formation and deposition of the α3α4α5 protomer into the glomerular basement membrane. In this issue, Yu etal. show that the chemical chaperone tauroursodeoxycholic acid prevented kidney structural changes and function decline in mice with a pathogenic missense Col4a3 mutation by increasing mutant α3α4α5 protomer glomerular basement membrane deposition and preventing podocyte apoptosis induced by endoplasmic reticulum stress.

Is Exon Skipping a Viable Therapeutic Approach for Vascular Ehlers-Danlos Syndrome with Mutations in COL3A1 Exon 10 or 15?

Vascular Ehlers-Danlos syndrome or Ehlers-Danlos syndrome type IV (vEDS) is a connective tissue disorder characterised by skin hyperextensibility, joint hypermobility and fatal vascular rupture caused by COL3A1 mutations that affect collagen III expression, homo-trimer assembly and secretion. Along with collagens I, II, V and XI, collagen III plays an important role in the extracellular matrix, particularly in the inner organs. To date, only symptomatic treatment for vEDS patients is available. Fibroblasts derived from vEDS patients carrying dominant negative and/or haploinsufficiency mutations in COL3A1 deposit reduced collagen III in the extracellular matrix. This study explored the potential of an antisense oligonucleotide (ASO)-mediated splice modulating strategy to bypass disease-causing COL3A1 mutations reported in the in-frame exons 10 and 15. Antisense oligonucleotides designed to redirect COL3A1 pre-mRNA processing and excise exons 10 or 15 were transfected into dermal fibroblasts derived from vEDS patients and a healthy control subject. Efficient exon 10 or 15 excision from the mature COL3A1 mRNA was achieved and intracellular collagen III expression was increased after treatment with ASOs; however, collagen III deposition into the extracellular matrix was reduced in patient cells. The region encoded by exon 10 includes a glycosylation site, and exon 15 encodes hydroxyproline and hydroxylysine-containing triplet repeats, predicted to be crucial for collagen III assembly. These results emphasize the importance of post-translational modification for collagen III homo-trimer assembly. In conclusion, while efficient skipping of target COL3A1 exons was achieved, the induced collagen III isoforms generated showed defects in extracellular matrix formation. While therapeutic ASO-mediated exon skipping is not indicated for the patients in this study, the observations are restricted to exons 10 and 15 and may not be applicable to other collagen III in-frame exons.

ГЕНЕТИЧЕСКАЯ ХАРАКТЕРИСТИКА Х-СЦЕПЛЕННОГО СИНДРОМА АЛЬПОРТА У ДЕТЕЙ: ДАННЫЕ ОДНОЦЕНТРОВОГО КОГОРТНОГО ИССЛЕДОВАНИЯ

X-linked Alport syndrome (XLAS) is a monogenic disease characterized by the progressive nephropathy development, sensorineural hearing loss and the lens and retina pathology. The clinical manifestations of the syndrome and the renal prognosis of patients are determined by the nature of the gene COL4A5 mutation. The range of COL4A5 genetic variants is different among populations. Information about the XLAS genetic structure in Russian pediatric cohort is insufficient. The purpose of this research was to determine the features of the spectrum of the gene COL4A5 genetic variants in children with XLAS. Materials and methods used: a single-center retrospective cohort study included children aged 2 to 17 y/o with genetically confirmed XLAS. Descriptions of variants in gene COL4A5 were performed using genome build GRCh37/hg19 in accordance with the reference sequence GRCh37/hg19 (Reference Sequence, HGVS) and the American College of Medical Genetics and Genomics (ACMG), AMP Clinical Practice Guidelines. Results: analysis of data from 174 probands from unrelated families showed that 108 (62%) children had missense variants in gene COL4A5 (62% v. 38%, missense v. non-missense variants, respectively, p=0.028), 24 (13.8%) had mutations leading to impaired RNA splicing, 17 (9.8%) had frameshift mutations, 14 (8%) had gene deletions and 10 (5.7%) had nonsense mutations. Missense variants were predominantly localized in the collagen domain compared to the non-collagen domain (n=102, 94.4%, p<0.001), in exons 18 to 41 (n=94; 94.8%) and were represented by glycine substitutions (n=90, 83.3%). Two common variants were identified in the cohort: NM_033380.3(COL4A5):c.1871G>A (p.Gly624Asp) in 28 (26%) and NM_033380.3(COL4A5):c.3319G>A (p.Gly1107Arg) in 4 (3.7%). Conclusion: the structure of COL4A5 genetic variants in the studied cohort was comparable with the current Worldwide data, such as two thirds of the examined had missense variants and ca. one-fifth had genetic variants leading to the protein synthesis absence. Two common missense variants in gene COL4A5 were identified, including the common variant NM_033380.3(COL4A5):c.1871G>A (p.Gly624Asp) that is of frequent occurrence in the European population.

Dystrophic epidermolysis bullosa characterized by mucosal lesions in a Chinese familial case with a novel compound heterozygous mutation of COL7A1.

Dystrophic epidermolysis bullosa (DEB) is a rare, but severe, subtype of epidermolysis bullosa. It is characterized mainly by blisters and miliary rashes of the skin, while oral mucosa-dominated cases are extremely rare. Here, we report the characteristics of oral mucosa lesions in a Chinese familial case of DEB with a novel compound heterozygous COL7A1 mutation. We further analyzed the genetic and molecular features of the proband and the two related mutation carriers. Our study further elucidates the genetic and phenotypic heterogeneity of DEB.

Targeted panel sequencing of pharmacogenes and oncodrivers in colorectal cancer patients reveals genes with prognostic significance

BackgroundColorectal cancer is still the second leading cause of cancer-related deaths and thus biomarkers allowing prediction of the resistance of patients to therapy and estimating their prognosis are needed. We designed a panel of 558 genes with pharmacogenomics records related to 5-fluorouracil resistance, genes important for sensitivity to other frequently used drugs, major oncodrivers, and actionable genes. We performed a target enrichment sequencing of DNA from tumors and matched blood samples of patients, and compared the results with patient prognosis stratified by systemic adjuvant chemotherapy.ResultsThe median number of detected variants per tumor sample was 18.5 with 4 classified as having a high predicted functional effect and 14.5 moderate effect. APC, TP53, and KRAS were the most frequent mutated genes (64%, 59%, and 42% of mutated samples, respectively) followed by FAT4 (23%), FBXW7, and PIK3CA (16% for both). Patients with advanced stage III had more frequently APC, TP53, or KRAS mutations than those in stages I or II. KRAS mutation counts followed an increasing trend with grade (G1 < G2 < G3). The response to adjuvant therapy was worse in carriers of frameshift mutations in APC or 12D variant in KRAS, but none of these oncodrivers had prognostic value. Carriage of somatic mutations in any of the genes ABCA13, ANK2, COL7A1, NAV3, or UNC80 had prognostic relevance for worse overall survival (OS) of all patients. In contrast, mutations in FLG, GLI3, or UNC80 were prognostic in the same direction for patients untreated, and mutations in COL6A3, LRP1B, NAV3, RYR1, RYR3, TCHH, or TENM4 for patients treated with adjuvant therapy. The first association was externally validated. From all germline variants with high or moderate predicted functional effects (median 326 per patient), > 5% frequency and positive Manhattan plot based on 3-year RFS, rs72753407 in NFACS, rs34621071 in ERBB4, and rs2444274 in RIF1 were significantly associated with RFS, OS or both.ConclusionsThe present study identified several putative somatic and germline genetic events with prognostic potential for colorectal cancer that should undergo functional characterization.

Three Familial Cases of Stickler Syndrome: A Case Report

Purpose: Stickler syndrome, a hereditary connective tissue disorder characterized by mutations in collagen genes, presents with progressive ophthalmopathy and diverse systemic manifestations. Here, we present three familial cases of Stickler syndrome, emphasizing the importance of early detection through clinical investigations and genetic testing.Case summary: Two generations of a family, a mother and her two daughters, were evaluated for Stickler syndrome. All three exhibited bilateral retinal lattice degeneration, perivascular retinal degeneration, and vitreous liquefaction. The daughters shared characteristic facial features, including a flattened face, broad nasal bridge, and micrognathia. Clinical symptoms and examination findings led to diagnoses of Stickler syndrome. Subsequent genetic testing in five family members confirmed a COL2A1 mutation in the three affected individuals.Conclusions: Stickler syndrome carries a high risk of vision loss from ocular complications, necessitating early detection and intervention. In addition, the presence of systemic manifestations, such as musculoskeletal joint disorders, mitral valve prolapse, hearing loss, and cleft palate, emphasizes the importance of prompt detection through appropriate clinical investigations and genetic testing.

Four novel mutations identified in the COL4A3, COL4A4 and COL4A5 genes in 10 families with Alport syndrome

BackgroundAlport syndrome (AS) is an inherited nephropathy caused by mutations in the type IV collagen genes. It is clinically characterized by damage to the eyes, ears and kidneys. Diagnosis of AS is hampered by its atypical clinical picture, particularly when the typical features, include persistent hematuria and microscopic changes in the glomerular basement membrane (GBM), are the only clinical manifestations in the patient.MethodsWe screened 10 families with suspected AS using whole exome sequencing (WES) and analyzed the harmfulness, conservation, and protein structure changes of mutated genes. In further, we performed in vitro functional analysis of two missense mutations in the COL4A5 gene (c.2359G > C, p.G787R and c.2605G > A, p.G869R).ResultsWe identified 11 pathogenic variants in the type IV collagen genes (COL4A3, COL4A4 and COL4A5). These pathogenic variants include eight missense mutations, two nonsense mutations and one frameshift mutation. Notably, Family 2 had digenic mutations in the COL4A3 (p.G1170A) and UMOD genes (p.M229K). Family 3 had a digenic missense mutation (p.G997E) in COL4A3 and a frameshift mutation (p.P502L fs*151) in COL4A4. To our knowledge, four of the 11 mutations are novel mutations. In addition, we found that COL4A5 mutation relation mRNA levels were significantly decreased in HEK 293 T cell compared to control, while the cellular localization remained the same.ConclusionsOur research expands the spectrum of COL4A3-5 pathogenic variants, which is helpful for clinical and scientific research.

Clinical spectrum of rare bone fragility disorders and response to bisphosphonate treatment: a retrospective study.

Osteogenesis Imperfecta (OI) is a clinically and genetically heterogeneous group of diseases characterized by brittle bones. Though genetic mutations in COL1A1 and COL1A2 account for approximately 85-90% of OI cases, there are now more than twenty genes described, responsible for rare forms of OI. Treatment is based on the use of bisphosphonates and though it is well established that they increase lumbar spine (LS) bone mineral density (BMD), the clinical impact on fracture reduction is still debated.In this study, we investigated the clinical characteristics of 38 patients with a bone fragility disorder that had variants in non-COL1A1/COL1A2 genes in order to study genotype-phenotype correlations, as the natural history of these rare forms is still not well known. We then studied the usefulness of bisphosphonate treatment by evaluating the effects on LS BMD, annual non-vertebral fracture rate, bone turnover markers and height. This study enabled us to better define the natural history of patients with non-COL1 pathogenic variants. Patients with CRTAP and TMEM38B variants consistently had a prenatal presentation with a short (<3rd p) and bowed femur. Importantly, this prenatal involvement does not predict the postnatal severity of the disease. Regarding treatment by bisphosphonates, all patients showed a significant increase in LS BMD while treated and this increase was dependent on the dose received. The increase in LS BMD also translated in a reduction of fracture rate during treatment. Finally, our study showed that the earlier bisphosphonates are initiated, the greater the fracture rate is reduced.

#3084 Familial nephropathy associated with a combined mutations of Alport and Nail Patella syndrome genes in the same family

Abstract Introduction Alport syndrome is a genetic condition stemming from mutation in Type IV collagen and is characterized by kidney disease and frequently hearing loss and ocular abnormalities. Renal involvement is from an abnormality of the glomerular basement membrane with hematuria and proteinuria progressing eventually to renal failure. In the vast majority, the inheritance is X- linked affecting the alpha 5 chain of type IV collagen while in about 15 percent of the patients the inheritance is autosomal recessive or dominant with mutations affecting alpha 3 or 4 chains of type IV collagen. Sensorineural deafness is common and ocular abnormalities may include lenticonus, corneal opacities, fleck retinopathy and temporal retinal thinning. Nail Patella syndrome (NPS) is a rare genetic condition from mutation in the LMX1B gene on chromosome 9 with an autosomal dominant inheritance. Glomerular disease is from characteristic glomerular basement membrane changes and is associated with nail, pelvic girdle and limb abnormalities. A forme fruste with glomerular lesions but lacking extrarenal features is recognized but uncommon. We present a family with mutations in both COL4A5 and LMX1B presenting with hematuria and proteinuria Case Presentation A 23 year old female was evaluated for hematuria and proteinuria. Her history was notable for kidney biopsy at the age thirteen showing focal and segmental glomerulosclerosis (FSGS). She was treated with tacrolimus for four years from age thirteen through seventeen. Patient was reportedly diagnosed with Nail Patella Syndrome after genetic testing. Her family history was notable for hematuria in her brother and hematuria and proteinuria in her mother. On physical examination she was noted to have no nail or skeletal abnormalities associated with Nail Patella Syndrome. Her labs were notable for a serum creatinine of 0.6 mg/dl and proteinuria of 155 mg/g creatinine of proteinuria. Urine microscopy revealed dysmorphic hematuria. Radiological imaging did not show skeletal abnormalities observed in Nail Patella Syndrome but genetic testing identified a pathogenic variant in COL4A5 c.919G&amp;gt;A (p.Gly307Ser) in addition to a variant of uncertain significance in LMX1B c.349G&amp;gt;A (p.Gly117Ser). Her brother aged 20 had a creatinine of 0.87 mg/dl with dysmorphic hematuria and no proteinuria. Genetic testing showed the same pathogenic variant in COL4A5 as in his sibling. His mother aged 55 was subsequently evaluated and had a creatinine 0.73 mg/dl with dysmorphic hematuria and 152 mg/g of proteinuria. Genetic testing was with the same variant in COL4A5 noted in her two children. Renal biopsy was extensive thinning and segmental lamellation of the glomerular basement membrane with eight percent FSGS. The typical “moth-eaten” appearance of the glomerular basement membrane characteristic of NPS was not evident. Segmental staining was observed with alpha 5 unit of Type IV collagen. Audiology and retinal optical coherence optometry studies are pending. Discussion Alport syndrome and Nail Patella Syndrome are rare genetic disorders that cause variable degrees of renal insufficiency from glomerular base membrane defects and are associated with characteristic extra renal manifestations. This is the first report of an inherited nephritis with combined mutations in COL4A5 and LMX1B. The clinical features and renal biopsy are compatible with Alport Syndrome and the significance of the mutation in LMX1B is uncertain. Conclusion This is the first case report of a combined mutation in COL4A5 and LMX1B gene presenting with hematuria and minimal proteinuria with preserved kidney function.