Heterozygous Deletion Of Exon Research Articles

Clinical and genetic analysis of autosomal dominant polycystic liver disease

Objective: To analyze and clarify the clinical and pathogenic gene variation and genetic etiology of polycystic liver disease. Methods: The proband clinical data and family history were collected. Whole-exome sequencing technology was used to detect the proband gene variations. Fluorescence quantitative PCR validation was performed on the proband and his family to screen out pathogenic gene variation. Results: A multiple liver cyst was found in an 18-year-old male proband during a physical examination. There were no abnormalities in his liver function, and both his father and grandfather had multiple liver cysts without any obvious discomfort or other special manifestations. Whole exome sequencing suggested a heterozygous deletion in exon 1 (Exon 1) of the SEC63 gene in the proband. Real-time fluorescence quantitative PCR confirmed that the heterozygous deletion variation of the SEC63 gene Exon 1 of the proband came from his father, and the same heterozygous deletion was detected in his grandfather. The gene variant had a pathogenic variation that had been rarely reported before and was in accordance with the the American college of Medical Genetics and Genomics (ACMG) guidelines. Conclusions: The genetic etiology of this autosomal dominant polycystic liver disease has been clarified, and the heterozygous deletion of Exon1 of the SEC63 gene is a newly discovered gene variation that broadens the variation spectrum of the SEC63 gene.

Clinical significance of Spinal Muscular Atrophy carrier detection in Guangdong Province, China: Insights from quantitative polymerase chain reaction and multiplex ligation-dependent probe amplification analysis

ObjectiveThis study aimed to identify carriers of Spinal Muscular Atrophy (SMA) among 10,630 pregnant women in Guangdong Province and provide prenatal diagnoses for high-risk fetuses from carrier couples. The goal was to prevent the birth of children affected by SMA. We evaluated the effectiveness of quantitative PCR (qPCR) and multiplex ligation-dependent probe amplification (MLPA) in detecting deletions in the SMN1 gene, with MLPA as the reference standard. MethodsFluorescent qPCR was used for initial SMA carrier screening, followed by confirmatory testing with MLPA for all detected carriers. ResultsOf the 10,630 women screened, 219 were identified as carriers (2.06 % detection rate). This included 17 cases of heterozygous deletion of exon 7 (E7), 145 cases with deletions of both E7 and exon 8 (E8), and 57 cases of E8 deletion alone. The carrier rate for E7 heterozygous deletion was established at 1.5 %. Prenatal diagnosis for seven carrier couples revealed five fetuses as carriers and one affected by SMA. The diagnostic concordance between qPCR and MLPA was 100 %. ConclusionThe combined use of qPCR and MLPA is vital in identifying SMA carriers, allowing for early diagnosis and informed reproductive decisions. The high sensitivity and specificity of qPCR, matching MLPA, demonstrate its value in clinical settings for SMA screening and prenatal diagnosis. Our findings emphasize the critical importance of selecting precise diagnostic methods to enhance clinical outcomes in genetic screening programs.

Identification of biallelic mutations in MCM3AP and comprehensive literature analysis.

Minichromosome maintenance complex component 3 associated protein (MCM3AP) is a gene in which mutations can result in autosomal recessive peripheral neuropathy with or without impaired intellectual development. The MCM3AP genotype-phenotype correlation and prognosis remain unclear. The aim of this study was to explore the genotype-phenotype correlations pertaining to MCM3AP. Whole-exome sequencing (WES) combined with copy number variation sequencing (CNV-seq) were performed on the genomic DNA isolated from a Chinese family, and Sanger sequencing, quantitative PCR and cDNA analyses were performed to examine the mutations. The retrospective study was conducted on 28 individuals with biallelic MCM3AP mutation-related diseases, including features such as mutations, motor development impairment, intellectual disability, weakness/atrophy, and cerebral magnetic resonance imaging abnormalities. Sequencing identified novel compound heterozygous mutations in MCM3AP, namely, a paternal variant c.1_5426del (loss of exons 1-25) and a maternal splicing variant c.1858 + 3A>G. Functional studies revealed that the variant c.1858 + 3A>G resulted in the heterozygous deletion of exon 5, thereby affecting splicing functionality. Furthermore, the compound heterozygous mutation may affect the functionality of the protein domain. Retrospective analysis revealed different genotype-phenotype correlations for the pathogenic variants in biallelic MCM3AP: all individuals (100%) with mutations outside the Sac3 domain exhibited early-onset symptoms, motor developmental delays, and cognitive abnormalities, conversely, the proportions of individuals carrying mutations within the domain were 26.7% (motor delays) and 46.7% (cognitive abnormalities). Our findings further expand the genetic mutation spectrum of biallelic MCM3AP and highlight the genotype-phenotype associations. Additionally, we elaborate on the importance of rehabilitation intervention.

Clinical, Genetic, and Histopathological Characteristics of CRX-associated Retinal Dystrophies

PURPOSETo describe phenotypic, genotypic, and histopathological features of inherited retinal dystrophies associated with the CRX gene (CRX-RDs). DESIGNRetrospective multicenter cohort study including histopathology. SUBJECTSThirty-nine patients from 31 families with pathogenic variants in the CRX gene. METHODSClinical data of 152 visits were collected from medical records with a median follow-up time of 9.1 years (IQR, 3.3-15.3 years; range, 0.0-48.8 years). Histopathologic examination of the eye of a 17-year-old patient with advanced early-onset CRX-RD was performed. MAIN OUTCOME MEASURESVisual acuity, retinal imaging, electroretinography (ERG), genotype-phenotype correlation, and histopathological examination were evaluated. RESULTSThe age at onset ranged from birth to the 8th decade of life. Median visual acuity was 1.00 logMAR (IQR, 0.69-1.48 logMAR; range, 0.06-3.00 logMAR) at a mean age of 52.0 ± 19.9 years (range, 4.6-81.9 years). Sufficient imaging was available for 36 out of 39 patients (92.3%), and all showed degeneration of at least the macula. Out of these 36 patients, 22 (61.1%) had only macular dystrophy. Another 10 patients (27.8%) had additional degeneration beyond the vascular arcades, and 4 patients (11.1%) panretinal degeneration. Two patients (5.1%) had Leber congenital amaurosis (LCA). In total, 21 different disease-associated heterozygous CRX variants were identified (10 missense, 8 frameshift, 2 deletion, 1 deletion-insertion variants). Missense variants in the CRX homeodomain and two variants deleting all functional domains, thus causing haploinsufficiency, generally tended to cause milder late-onset phenotypes.Histopathologic examination of the eye of a 17-year-old patient with advanced early-onset retinal dystrophy due to a heterozygous deletion of exons 3 and 4 of the CRX gene revealed loss of laminar integrity and widespread photoreceptor degeneration especially in the central retina, with extensive loss of photoreceptor nuclei and outer segments. CONCLUSIONThis study illustrates the large clinical and genetic heterogenic spectrum of CRX-RDs, ranging from LCA to mild late-onset maculopathy resembling occult macular dystrophy. Haploinsufficiency and missense variants tended to be associated with milder phenotypes. Patients showed degeneration predominantly affecting the central retina on imaging. The histopathological findings also mirror these clinical findings and features similar to previously reported animal models of CRX-RDs.

The application value of whole exome sequencing technology in diagnosis of hereditary renal cysts

The data of 57 renal cyst patients who visited the First Affiliated Hospital of Zhengzhou University from January 2023 to March 2024 were retrospectively analyzed. The age of patients ranged from three months to 60 years old, with 31 males and 26 females. The whole exome sequencing (WES) detected pathogenic or suspected pathogenic (P/LP) variants in 48 renal cystic probands, with a detection rate of 84.2% (48/57), including PKD1, PKD2, PKHD1, LRP5, COL4A4 and ALG8 gene variants as well as copy number variations (CNV). In addition, four PKD1 gene variants of uncertain significance (VUS) were detected. In five WES negative families, one PKD1 nonsense variation was detected through long-range PCR (LR-PCR)+Oxford nanopore technologies, and one heterozygous deletion in exon 22 of PKD1 gene was detected through multiplex ligation-dependent probe amplification (MLPA). In summary, WES can detect multiple types of variations, which is helpful for early diagnosis and prognosis prediction of renal cyst patients. However, there is still a risk of failing to detect PKD1 gene by WES, therefore, healthcare practitioners should beware of the negative results of WES.

Genetic analysis and prenatal diagnosis for a Chinese pedigree affected with co-morbid Ornithine carbamoyl transferase deficiency and MECP2 duplication syndrome

To explore the genetic basis for a Chinese pedigree affected with co-morbid Ornithine carbamoyl transferase deficiency (OTCD) and MECP2 duplication syndrome. A proband who was admitted to the Neonatal Intensive Care Unit of Gansu Provincial Maternal and Child Health Care Hospital on December 19, 2017 was selected as the study subject. High-throughput sequencing and multiplex ligation-dependent probe amplification (MLPA) were carried out for her pedigree, and short tandem repeat-based linkage analysis and chromosome copy number variation sequencing (CNV-seq) were used for the prenatal diagnosis. The proband, a 3-day-old female, was found to harbor heterozygous deletion of exons 7-9 of the OTC gene. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the variant was classified as likely pathogenic (PVS1+PM2_Supporting+PP4). The proband was diagnosed with OTCD , which was in keeping with her acute encephalopathy and metabolic abnormalities (manifesting as hyperammonemia, decreased blood citrulline, and increased urine orotic acid). Prenatal diagnosis was carried out for the subsequent pregnancy. The fetus did not harbor the exons 7-9 deletion of the OTC gene, but was found to carry a duplication in Xq28 region (which encompassed the whole region of MECP2 duplication syndrome) and was positive for the SRY sequence. The same duplication was also found in the proband and her mother. Considering the possible existence of X-chromosome inactivation, the proband was diagnosed with two X-linked recessive disorders including OTCD and MECP2 duplication syndrome, and the fetus was determined as a male affected with the MECP2 duplication syndrome. Discoveries of the pathogenic variants underlying the OTCD and MECP2 duplication syndrome have enabled clinical intervention, treatment, genetic counseling and prenatal diagnosis for this pedigree.

Complex analysis of the national Hereditary angioedema cohort in Slovakia – Identification of 12 novel variants in SERPING1 gene

BackgroundHereditary angioedema (HAE) is a rare autosomal dominant genetic disease characterised by acute episodes of non-pruritic skin and submucosal swelling caused by increase in vascular permeability. ObjectiveHere we present the first complex analysis of the National HAE Slovakian cohort with the detection of 12 previously un-published genetic variants in SERPING1 gene. MethodsIn patients diagnosed with hereditary angioedema caused by deficiency or dysfunction of C1 inhibitor (C1–INH-HAE) based on clinical manifestation and complement measurements, SERPING1 gene was tested by DNA sequencing (Sanger sequencing/massive parallel sequencing) and/or multiplex ligation-dependent probe amplification for detection of large rearrangements. ResultsThe Slovakian national cohort consisted of 132 living patients with confirmed HAE. We identified 51 index cases (32 families, 19 sporadic patients/112 adults, 20 children). One hundred seventeen patients had HAE caused by deficiency of C1 inhibitor (C1–INH-HAE-1) and 15 patients had HAE caused by dysfunction of C1 inhibitor (C1–INH-HAE-2). The prevalence of HAE in Slovakia has recently been calculated to 1:41 280 which is higher than average calculated prevalence. The estimated incidence was 1:1360 000. Molecular-genetic testing of the SERPING1 gene found 22 unique causal variants in 26 index cases, including 12 previously undescribed and unreported. ConclusionThe first complex report about epidemiology and genetics of the Slovakian national HAE cohort expands the knowledge of the C1–INH-HAE genetics. Twelve novel causal variants were present in the half of the index cases. A higher percentage of inframe variants comparing to other studies was observed. Heterozygous deletion of exon 3 found in a large C1–INH-HAE-1 family probably causes the dysregulation of the splicing isoforms balance and leads to the decrease of full-length C1–INH level.

A large deletion in TSC2 causes tuberous sclerosis complex by dysregulating PI3K/AKT/mTOR signaling pathway

Background/aimTuberous sclerosis complex (TSC) is a multi-system syndrome caused by loss-of-function mutation in TSC1 or TSC2. Most TSC patients present with cardiac rhabdomyoma or cortical tubers during fetal life, and the symptoms are not uniform as their age. The gene products of TSC1/2 are components of the TSC protein complex and are important role in the PI3K/AKT/mTOR (PAM) signaling pathway. Based on three members of a family with variable expressivity, the purpose of this study was to clarify the clinical features of TSC in different age groups and to analyze the genetic characteristics of TSC2 gene. MethodsClinical exome sequencing and co-segregation were used to identify a three-generation family with four affected individuals. HEK-293T cell model was constructed for subsequent experiments. Quantitative RT-PCR, western blotting, and subcellular localization were used to analyze the expression effect of TSC2 mutation. CCK-8 assay, wound healing assay, and cell cycle analysis were used to analyze the function effect of TSC2 mutation. ResultWe identified a TSC family with heterozygous deletion of exon 4 in TSC2 by clinical exon sequencing. Sanger sequencing indicated that the affected individuals have 2541-bp deletion that encompassed exon 4 and adjacent introns. Deletion of exon 4 decreased the TSC2 mRNA and protein levels in HEK-293T cells, and activated the PI3K/AKT/mTOR pathway, thereby altering the cell cycle and promoting cell proliferation and migration. ConclusionWe confirmed the pathogenicity of the large deletion in TSC2 in a three- generations family.. Deletion of exon 4 of TSC2 affected cell proliferation, migration, and cell cycle via abnormal activation of the PAM pathway. This study evaluated the pathogenic effect of deletion of exon 4 of TSC2 and investigated the underlying mechanism.

Unfavorable switching of skewed X chromosome inactivation leads to Menkes disease in a female infant

Menkes disease is an X-linked disorder of copper metabolism caused by mutations in the ATP7A gene, and female carriers are usually asymptomatic. We describe a 7-month-old female patient with severe intellectual disability, epilepsy, and low levels of serum copper and ceruloplasmin. While heterozygous deletion of exons 16 and 17 of the ATP7A gene was detected in the proband, her mother, and her grandmother, only the proband suffered from Menkes disease clinically. Intriguingly, X chromosome inactivation (XCI) analysis demonstrated that the grandmother and the mother showed skewing of XCI toward the allele with the ATP7A deletion and that the proband had extremely skewed XCI toward the normal allele, resulting in exclusive expression of the pathogenic ATP7A mRNA transcripts. Expression bias analysis and recombination mapping of the X chromosome by the combination of whole genome and RNA sequencing demonstrated that meiotic recombination occurred at Xp21-p22 and Xq26-q28. Assuming that a genetic factor on the X chromosome enhanced or suppressed XCI of its allele, the factor must be on either of the two distal regions derived from her grandfather. Although we were unable to fully uncover the molecular mechanism, we concluded that unfavorable switching of skewed XCI caused Menkes disease in the proband.

Copy Number Variations in Hereditary Spastic Paraplegia-Related Genes: Evaluation of an Iranian Hereditary Spastic Paraplegia Cohort and Literature Review

Introduction: In human genetic disorders, copy number variations (CNVs) are considered a considerable underlying cause. CNVs are generally detected by array-based methods but can also be discovered by read-depth analysis of whole-exome sequencing (WES) data. We performed WES-based CNV identification in a cohort of 35 Iranian families with hereditary spastic paraplegia (HSP) patients. Methods: Thirty-five patients whose routine single-nucleotide variants (SNVs) and insertion/deletion analyses from exome data were unrevealing underwent a pipeline of CNV analysis using the read-depth detection method. Subsequently, a comprehensive search about the existence of CNVs in all 84 known HSP-causing genes was carried out in all reported HSP cases, so far. Results and Discussion: CNV analysis of exome data indicated that 1 patient harbored a heterozygous deletion in exon 17 of the SPAST gene. Multiplex ligation-dependent probe amplification analysis confirmed this deletion in the proband and his affected father. Literature review demonstrated that, to date, pathogenic CNVs have been identified in 30 out of 84 HSP-causing genes (∼36%). However, CNVs in only 17 of these genes were specifically associated with the HSP phenotype. Among them, CNVs were more common in L1CAM, PLP1, SPAST, SPG7, SPG11, and REEP1 genes. The identification of the CNV in 1 of our patients suggests that WES allows the detection of both SNVs and CNVs from a single method without additional costs and execution time. However, because of intrinsic issues of WES in the detection of large rearrangements, it may not yet be exploited to replace the CNV detection methods in standard clinical practice.

Genetic analysis of a child with Charlevoix-Saguenay spastic ataxia due to variant of SACS gene

To explore the clinical feature and genetic variant of a child with autosomal recessive Charlevoix-Saguenay type spastic ataxia (ARSACS). Clinical data of a child who was admitted to the West China Second Hospital of Sichuan University on April 30, 2021 was collected. Whole exome sequencing (WES) was carried out for the child and his parents. Candidate variants were verified by Sanger sequencing and bioinformatic analysis based on the guidelines from the American College of Medical Genetics and Genomics (ACMG). The child, a 3-year-and-3-month-old female, had a complain of "walking instability for over a year". Physical and laboratory examination revealed progressive and aggravated gait instability, increased muscle tone of the right limbs, peripheral neuropathy of the lower limbs, and thickening of retinal nerve fiber layer. The results of WES revealed that she has harbored a maternally derived heterozygous deletion of exons 1 to 10 of the SACS gene, in addition with a de novo heterozygous c.3328dupA variant in exon 10 of the SACS gene. Based on the ACMG guidelines, the exons 1-10 deletion was rated as likely pathogenic (PVS1+PM2_Supporting), and the c.3328dupA was rated as a pathogenic variant (PVS1_Strong+PS2+PM2_Supporting). Neither variant was recorded in the human population databases. The c.3328dupA variant and the deletion of exons 1-10 of the SACS gene probably underlay the ARSACS in this patient.

Immunodeficiency in a female patient with Incontinentia Pigmenti

Incontinentia pigmenti (IP) is a rare X-linked dominant neuroectodermal disorder characterized by ocular, dermatologic, and neurological abnormalities. It is caused by heterozygous mutations in IKBKG (NEMO), which encodes a regulatory factor involved in NF-kB activation. Random and skewed X-inactivation allows for female survival and determines extent of disease. Although immune function is typically normal in IP patients, hypomorphic IKBKG mutations are known to cause immunodeficiency, as occurs in X-linked NEMO deficiency. A female newborn presented with bullous vesicles, peeling skin, alopecia, hearing loss, and tonic-clonic seizures with MRI demonstrating evidence of in utero stroke. She developed intermittent fevers and cellulitis and was diagnosed with IP based on clinical findings. Following discharge, she was readmitted at 1 month of age due to bronchiolitis complicated by pulmonary abscess. Labs demonstrated hyperleukocytosis with hypereosinophilia, normal T, B, and NK lymphocyte enumeration, abnormal lymphocyte proliferation to phytohemagglutinin (PHA) and anti-CD3, and abnormal toll-like receptor (TLR) function. Genetic analysis revealed a heterozygous deletion of exons 4–10 in IKBKG. Labs at 1 year follow up showed normal lymphocyte (T, B, and NK) enumeration and mitogen responses, normal immunoglobulin levels, and normal responses to pneumococcal and tetanus vaccines. While about 70% of IP patients harbor a deletion of exons 4–10 in IKBKG. unlike other hypomorphic NEMO mutations, this mutation is not typically associated with altered immune function. This case highlights that immunodeficiency may be an early clinical manifestation in female patients with IP.

Modeling incomplete penetrance in arrhythmogenic cardiomyopathy by human induced pluripotent stem cell derived cardiomyocytes

Human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) are commonly used to model arrhythmogenic cardiomyopathy (ACM), a heritable cardiac disease characterized by severe ventricular arrhythmias, fibrofatty myocardial replacement and progressive ventricular dysfunction. Although ACM is inherited as an autosomal dominant disease, incomplete penetrance and variable expressivity are extremely common, resulting in different clinical manifestations. Here, we propose hiPSC-CMs as a powerful in vitro model to study incomplete penetrance in ACM. Six hiPSC lines were generated from blood samples of three ACM patients carrying a heterozygous deletion of exon 4 in the PKP2 gene, two asymptomatic (ASY) carriers of the same mutation and one healthy control (CTR), all belonging to the same family. Whole exome sequencing was performed in all family members and hiPSC-CMs were examined by ddPCR, western blot, Wes™ immunoassay system, patch clamp, immunofluorescence and RNASeq. Our results show molecular and functional differences between ACM and ASY hiPSC-CMs, including a higher amount of mutated PKP2 mRNA, a lower expression of the connexin-43 protein, a lower overall density of sodium current, a higher intracellular lipid accumulation and sarcomere disorganization in ACM compared to ASY hiPSC-CMs. Differentially expressed genes were also found, supporting a predisposition for a fatty phenotype in ACM hiPSC-CMs. These data indicate that hiPSC-CMs are a suitable model to study incomplete penetrance in ACM.

Recurrent posterior fossa group A (PFA) ependymoma in a young child with constitutional mismatch repair deficiency (CMMRD).

Recurrent posterior fossa group A (PFA) ependymoma in a young child with constitutional mismatch repair deficiency (CMMRD).

Prenatal diagnosis of partial deletion of NRXN1 gene with combined CNV-seq and qPCR assays

To summarize the genetic diagnosis, low-depth copy number variation sequencing (CNV-seq) and prenatal finding in 7 fetuses with 2p16.3 deletions only involving the NRXN1 gene. The 7 fetuses have all been found to have loss of heterozygosity at 2p16.3 by CNV-seq, which were verified by quantitative real-time PCR (qPCR). Specific regions of NRXN1 gene deletions were identified, and the CNVs were verified in their parents. Outcome of the pregnancies were followed up. Among 16 502 prenatal samples, 7 fetuses were found to harbor a 120 kb ~ 900 kb microdeletion in the 2p16.3 region, which yielded a prevalence of 0.424‰. The deleted region mainly involved 50 200 000-51 880 000 positions of chromosome 2 and involved only the NRXN1 gene. All of the 7 fetal CNVs were confirmed by qPCR, including 2 cases with heterozygous deletion of exons 1 to 6, 1 with heterozygous deletion of exons 1 to 19, 1 with heterozygous deletion of exons 19 to 22, and 3 with heterozygous deletion of introns 6 to 7 of the NRXN1 gene. Verification in the parents had found that one deletion was inherited from the father, 1 was from the mother, 2 cases were de novo in origin, whilst the remaining 3 had refused parental verification. After genetic counseling, one couple had elected induced abortion, 1 case has not been born yet, whilst the other 5 cases were born healthy. Follow up had identified no mental abnormalities among the children. Seven fetuses with heterozygous 2p16.3 deletions only involving the NRXN1 gene were detected by CNV-seq. The specific deletion of the NRXN1 gene was verified by qPCR. Prenatal genetic counseling and fertility guidance has been provided to the particular family by combining the results of CNV testing, pedigree analysis and pregnancy outcome.

Intrafamilial phenotypic variability in autosomal recessive DOCK6-related Adams-Oliver syndrome

Adams-Oliver syndrome (AOS) is diagnosed in presence of aplasia cutis congenita (ACC) of the scalp and terminal transverse limb defects (TTLD). The autosomal recessive (AR) DOCK6-related form of AOS is most often associated with a severe phenotype including also central nervous system and ocular abnormalities. We report a sister and brother with different expression of the phenotype. Both were compound heterozygous pathogenic variants in the DOCK6 gene, including a heterozygous c.5939+2T > C intronic variant that was maternally inherited, and a heterozygous deletion of exons 10 to 21 that was paternally inherited. The sister had microcephaly, periventricular calcifications, minor retinal vasculopathy, and mild impaired neurodevelopment, but only very subtle limb abnormalities and no ACC. Her brother showed a classical DOCK6-related AOS phenotype, including a severe bilateral peripheral ischemic retinopathy. From a review of 22 molecularly confirmed cases with DOCK6-related AOS with ophthalmic examination, we found that 16 of them had retinal vascular pathology (72.7%), confirming as the major ocular anomaly. Documented intrafamilial variability in our family and the evidence revised from previous reports, confirm that AR DOCK6-related AOS expressivity can produce a “milder” phenotype without ACC or TTLD, which could be underdiagnosed in simplex cases because it is difficult to recognize out of a familial context. Therefore, in order to know its real magnitude is required the future inclusion of DOCK6 gene in NGS panels directed to the study of simplex cases of patients with microcephaly, periventricular calcifications, retinal vasculopathy, and/or cardiovascular defects.

P.15 Symptomatic DMD carrier as a differential diagnosis in patients presenting asymmetrical limb weakness

Duchenne/Becker muscular dystrophy (DMD) is one of the most common myopathies, characterized by an X-linked recessive disease. Asymmetrical limb weakness is rarely present in patients with muscle diseases such as ANO5-related myopathy, facioscapulohumeral muscular dystrophy, and sporadic inclusion body myositis. We report two cases of symptomatic DMD carriers presenting with asymmetrical limb weakness. A 50-year-old woman visited the department of neurology presenting with slowly progressive weakness of the limbs since childhood. A neurological examination revealed a weakness of the right arm and both legs, which were graded 4 as MRC system. Muscle MRI showed asymmetric fatty infiltration of the limbs, markedly affected by right biceps brachii, latissimus dorsi, and gastrocnemius. Immunohistochemistry (IHC) of the C-terminal region of the dystrophin gene presented several scattered stain-negative fibers. Genetic analysis revealed c.6703delG (p.Ser2235Ilefs*12, NM_004006.2) mimicking single exon 46 deletion in MLPA. A 29-year-old female presented with an elevated level of serum creatine kinase without subjective weakness. Neurologic examination showed the subtle motor weakness of the right arm, graded 4+. Muscle MRI revealed high T1 signal change on the right biceps femoris, which was not affected clinically, in addition to right biceps brachii and latissimus dorsi. IHC showed dystrophic changes and a mosaic pattern of dystrophin expression. The diagnosis was confirmed by MLPA, revealing heterozygous deletion of exon 44 in the DMD gene. Asymmetrical limb weakness can be a remark for the diagnosis of symptomatic DMD carrier. Furthermore, muscle MRI is more sensitive in detecting pathologic changes than routine neurologic examination. And single-base point mutation can mimick the exon deletion in MLPA, which needs sequencing analysis in a case of single exon deletion in DMD. Therefore, a multidisciplinary approach is mandatory for final diagnosis and a better understanding of symptomatic DMD carriers.

Von Hippel–Lindau (VHL) disease and VHL-associated tumors in Indian subjects: VHL gene testing in a resource constraint setting

BackgroundVon Hippel–Lindau (VHL) syndrome is a familial cancer syndrome caused by mutations in VHL gene. It is characterized by the formation of benign and malignant tumors like retinal angioma, cerebellar hemangioblastoma, spinal hemangioblastoma, renal cell carcinoma, pheochromocytoma, pancreatic and renal cysts, and endolymphatic sac tumors. Germline mutations in VHL gene have also been reported in isolated VHL-associated tumors. VHL gene is a small gene with 3 coding exons and can be easily tested even in a resource constraint setting.ObjectiveTo describe clinical presentation and estimate the diagnostic yield of in VHL and VHL-associated tumors.MethodsThis is a descriptive study in a hospital setting. Here, we describe the clinical and molecular data of 69 patients with suspected VHL or having VHL-associated tumors. Sanger sequencing of coding sequences and conserved splice sites of VHL gene were done in all patients. Multiplex ligation-dependent probe amplification (MLPA) of VHL gene to detect large deletions/duplications was performed for 18 patients with no pathogenic sequence variations.ResultsAmong tumor types at presentation, pheochromocytoma was seen in 49% (34/69), hemangioblastoma was seen in 30% (21/69), and renal cell carcinoma was seen in 7% (5/69). Rest had other tumors like paraganglioma, endolymphatic sac papillary tumors, cerebellar astrocytoma and pancreatic cyst. Seven patients (10%) had more than one tumor at the time of diagnosis. Pathogenic variations in VHL gene were identified in 31probands by Sanger sequencing; 18 were missense, 2 nonsense and 2 small indels. A heterozygous deletion of exon 3 was detected by MLPA in one patient among 18 patients for whom MLPA was done. Overall, the molecular yield was 46% cases (32/69). Family history was present in 7 mutation positive cases (22%). Overall, 11 families (16%) opted for pre-symptomatic mutation testing in the family.ConclusionsMutation testing is indicated in VHL and VHL-associated tumors. The testing facility is easy and can be adopted easily in developing countries like India. The yield is good, and with fairly high incidence of familial cases, molecular testing can help in pre-symptomatic testing and surveillance.

Analysis of pathogenic gene variant in two children with Treacher-Collins syndrome

To explore the clinical and genetic characteristics of two children with a clinical diagnosis of Treacher Collins syndrome (TCS). Whole-exome sequencing was used to screen potential variants in the two children. Confirmation of suspected variants was performed through Sanger sequencing, multiplex ligation dependent probe amplification and real-time PCR in probands and their parents. A heterozygous deletion variant, c.4357_4360delGAAA, was detected in case one, while was de novo and verified by Sanger sequencing. The variant was classified as pathogenic (PVS1 +PM2+PM6) according to ACMG guideline. The heterozygous deletion of exon 1-7 was seen in the same gene in case 2, which MLPA verified as heterozygous deletion of exon 1-6. This deletion was inherited from the father with a normal phenotype, and the father's TCOF1 gene was suspected to be chimeric heterozygous deletion of exon 1-6 verified by MLPA. The identified variants in the TCOF1 gene probably underlie the two cases of TCS. There was no apparent correlation between genotype and phenotype. In addition, it shows a high interfamilial variability ranging from normal to full presentation of TCS. Genetic detection provided clinical diagnosis and genetic counselling for TCS patients.

Targeted copy number variant identification across the neurodegenerative disease spectrum.

BackgroundAlthough genetic factors are known to contribute to neurodegenerative disease susceptibility, there remains a large amount of heritability unaccounted for across the diagnoses. Copy number variants (CNVs) contribute to these phenotypes, but their presence and influence on disease state remains relatively understudied.MethodsHere, we applied a depth of coverage approach to detect CNVs in 80 genes previously associated with neurodegenerative disease within participants of the Ontario Neurodegenerative Disease Research Initiative (n = 519).ResultsIn total, we identified and validated four CNVs in the cohort, including: (1) a heterozygous deletion of exon 5 in OPTN in an Alzheimer's disease participant; (2) a duplication of exons 1–5 in PARK7 in an amyotrophic lateral sclerosis participant; (3) a duplication of >3 Mb, which encompassed ABCC6, in a cerebrovascular disease (CVD) participant; and (4) a duplication of exons 7–11 in SAMHD1 in a mild cognitive impairment participant. We also identified 43 additional CNVs that may be candidates for future replication studies.ConclusionThe identification of the CNVs suggests a portion of the apparent missing heritability of the phenotypes may be due to these structural variants, and their assessment is imperative for a thorough understanding of the genetic spectrum of neurodegeneration.