Clinical and genetic characterization of a large cohort of Chinese patients with Bietti crystalline retinopathy.

PURPOSE: To investigate the clinical and genetic characteristics for a large cohort of Chinese patients with Bietti crystalline retinopathy (BCR). METHODS: A total of 208 Chinese BCR patients from 175 families were recruited. Comprehensive clinical evaluations and genetic analysis were performed. Genotype-phenotype correlations were evaluated through statistical analysis. RESULTS: The patients' median age was 37 years (range, 20-76 years). The median best corrected visual acuity (BCVA) was 0.8 LogMAR unit (range, 2.8 to -0.12). A significant decline of BCVA was revealed in patients over 40 years old (P<0.001). Two clinical types were observed: peripheral type (type P) and central type (type C). Significantly more type C patients had a worse central visual acuity, but a more preserved retinal function (P<0.05). Molecular screening detected biallelic CYP4V2 pathogenic variants in 98.3% (172/175) of the families, including 19 novel ones. The most frequent pathogenic variant was c.802-8_810del17insGC, with the allele frequency of 55.7% (195/350), followed by c.992A>C (28/350, 8%) and c.1091-2A>G (23/350, 6.6%). BCR patients with one c.802-8_810del17insGC and one truncating variant (IVS6-8/Tru) had BCVA>1.3 LogMAR unit (Snellen equivalent<20/400) at a younger age than those with homozygous c.802-8_810del17insGC variants (homo IVS6-8) (P=0.031). CONCLUSIONS: BCR patients preserved relatively good vision before 40 years old. Two distinct clinical types of BCR were observed. BCR patients with IVS6-8/Tru had an earlier decline in visual acuity than those with homo IVS6-8. Our findings enhance the knowledge of BCR and will be helpful in patient selection for gene therapy.

FDXR-associated disease in a Chinese cohort: Unraveling expanded ocular phenotypes and genetic spectrum.

FDXR: associated disease is characterized by optic atrophy, acoustic neuropathy, and developmental delays. This study evaluated the ocular phenotypes and genetic features of patients with biallelic FDXR variants. Five individuals from unrelated non-consanguineous Chinese families with biallelic FDXR variants were identified using whole exome sequencing, Sanger sequencing, and co-segregation validation. In addition to optic atrophy and diverse extraocular manifestations, all patients presented with retinal dystrophy, and electroretinogram showed severely impaired cone and rod functions in their first decades. Three of the five patients showed attenuated retinal vessels that appeared as white lines on the fundus, and fundus fluorescein angiography (FFA) further revealed vascular abnormalities including delayed filling, completely occluded retinal vasculature, and severe retinal vascular nonperfusion of the peripheral retina. Five novel FDXR variants were identified: c.383C > T (p.A128V), c.963delG (p.R322fs*7), c.1052_1053delTC (p.L351Pfs*12), c.394-11T > G and c.1002+1G > A. Retinal dystrophy with attenuated retinal vessels appearing as white lines was observed in this cohort, and the FFA images revealed that retinal vascular occlusion could be a distinct clinical characteristic of FDXR-associated disease. Probands with FDXR revealed severe early onset ophthalmic features with rapid-progression, indicating the importance of early diagnosis and treatment. Moreover, this is the first study to report FFA manifestations in an FDXR cohort, expanding the FDXR-associated ocular disease phenotype and genetic spectrum.

A deletion variant Arg616 of androgen receptor in a Chinese family with complete androgen insensitivity syndrome.

Background: Complete androgen insensitivity syndrome (CAIS, OMIM; 300068) is a disorder of sex development with X-linked recessive inheritance. Cases of CAIS usually present as female phenotype, with primary amenorrhea and/or inguinal hernia. Family aggregation is a rare scenario. Methods: This study is a retrospective analysis of CAIS cases in a three-generation pedigree. The patients' genomes were determined by sequencing the androgen receptor (AR) gene. The clinical data of the patients, including manifestations, hormone levels, and AR variants, were analyzed. Results: Sixteen people in this family were involved. A deletion variant (c.1847_1849del; p. Arg616del) was identified in exon 3 of AR, which encodes the DNA binding domain. Until now, four patients and four carriers have been identified in three generations of this family. All the patients live as female, and one has developed gonadal malignancy. Conclusion: The present study identified a deletion variant in three generations of a family with CAIS, including four carriers and four patients. This study verified the genetic pattern and the corresponding clinical characteristics of CAIS. Furthermore, a case with gonadal malignancy was discovered. The information on diagnosis and treatment in this pedigree is useful for prenatal diagnosis and genetic counseling of similar families.

Systematic assessment of the contribution of structural variants to inherited retinal diseases.

Despite increasing success in determining genetic diagnosis for patients with inherited retinal diseases (IRDs), mutations in about 30% of the IRD cases remain unclear or unsettled after targeted gene panel or whole exome sequencing. In this study, we aimed to investigate the contributions of structural variants (SVs) to settling the molecular diagnosis of IRD with whole-genome sequencing (WGS). A cohort of 755 IRD patients whose pathogenic mutations remain undefined was subjected to WGS. Four SV calling algorithms including include MANTA, DELLY, LUMPY, and CNVnator were used to detect SVs throughout the genome. All SVs identified by any one of these four algorithms were included for further analysis. AnnotSV was used to annotate these SVs. SVs that overlap with known IRD-associated genes were examined with sequencing coverage, junction reads, and discordant read pairs. PCR followed by Sanger sequencing was used to further confirm the SVs and identify the breakpoints. Segregation of the candidate pathogenic alleles with the disease was performed when possible. In total, sixteen candidate pathogenic SVs were identified in sixteen families, including deletions and inversions, representing 2.1% of patients with previously unsolved IRDs. Autosomal dominant, autosomal recessive, and X-linked inheritance of disease-causing SVs were observed in 12 different genes. Among these, SVs in CLN3, EYS, PRPF31 were found in multiple families. Our study suggests that the contribution of SVs detected by short-read WGS is about 0.25% of our IRD patient cohort and is significantly lower than that of single nucleotide changes and small insertions and deletions.

Systematic assessment of the contribution of structural variants to inherited retinal diseases.

Despite increasing success in determining genetic diagnosis for patients with inherited retinal diseases (IRDs), mutations in about 30% of the IRD cases remain unclear or unsettled after targeted gene panel or whole exome sequencing. In this study, we aimed to investigate the contributions of structural variants (SVs) to settling the molecular diagnosis of IRD with whole-genome sequencing (WGS). A cohort of 755 IRD patients whose pathogenic mutations remain undefined were subjected to WGS. Four SV calling algorithms including include MANTA, DELLY, LUMPY and CNVnator were used to detect SVs throughout the genome. All SVs identified by any one of these four algorithms were included for further analysis. AnnotSV was used to annotate these SVs. SVs that overlap with known IRD-associated genes were examined with sequencing coverage, junction reads and discordant read pairs. Polymerase Chain Reaction (PCR) followed by Sanger sequencing was used to further confirm the SVs and identify the breakpoints. Segregation of the candidate pathogenic alleles with the disease was performed when possible. A total of 16 candidate pathogenic SVs were identified in 16 families, including deletions and inversions, representing 2.1% of patients with previously unsolved IRDs. Autosomal dominant, autosomal recessive and X-linked inheritance of disease-causing SVs were observed in 12 different genes. Among these, SVs in CLN3, EYS and PRPF31 were found in multiple families. Our study suggests that the contribution of SVs detected by short-read WGS is about 0.25% of our IRD patient cohort and is significantly lower than that of single nucleotide changes and small insertions and deletions.

Phenotypic and genetic characteristics of 130 patients with mucopolysaccharidosis type II: A single-center retrospective study in China.

Background: Mucopolysaccharidosis Type II (MPS II) is a rare, progressive and ultimately fatal X-linked lysosomal storage disorder caused by mutations in the iduronate-2-sulfatase (IDS) gene. This report conducted a retrospective analysis to investigate the clinical characteristics, genotypes and management strategies in a large cohort of Chinese patients with MPS II. Methods: In this study, we explored 130 Chinese patients with MPS II between September 2008 and April 2022. Clinical manifestations, auxiliary examination, IDS pathogenic gene variants and IDS enzyme activity, surgical history were analysed in the study. Results: A total of 130 patients were enrolled and the mean age at diagnosis was 5 years old. This study found the most common symptoms in our patients were claw-like hands, followed by coarse facial features, birthmarks (Mongolian spot), delayed development, inguinal or umbilical hernia. The most commonly cardiac manifestations were valve abnormalities, which were mitral/tricuspid valve regurgitation (71.9%) and aortic/pulmonary valve regurgitation (36.8%). We had found 43 different IDS pathogenic gene variants in 55 patients, included 16 novel variants. The variants were concentrated in exon 9 (20% = 11/55), exon 3 (20% = 11/55) and exon 8 (15% = 8/55). A total of 50 patients (38.5%) underwent surgical treatment, receiving a total of 63 surgeries. The average age of first surgery was 2.6 years, and the majority of surgery (85.7%, 54/63) was operated before 4 years old. The most common and earliest surgery was hernia repair. Three patients were died of respiratory failure. Conclusion: This study provided additional information on the clinical, cardiac ultrasound and surgical procedure in MPS II patients. Our study expanded the genotype spectrum of MPS II. Based on these data, characterization of MPS II patients group could be used to early diagnosis and treatment of the disease.

Identification and characterization of two DMD pedigrees with large inversion mutations based on a long-read sequencing pipeline.

Pathogenic large inversions are rarely reported on DMD gene due to the lack of effective detection methods. Here we report two DMD pedigrees and proposed a reliable pipeline to define large inversions in DMD patients. In the first pedigree, conventional approaches including multiplex ligation-dependent probe amplification, and whole-exome sequencing by next generation sequencing were failed to detect any pathologic variant. Then an advanced analysis pipeline which consists of RNA-seq, cDNA array capture sequencing, optical mapping, long-read sequencing was built. RNA-seq and cDNA capture sequencing showed a complete absence of transcripts of exons 3-55. Optical mapping identified a 55 Mb pericentric inversion between Xp21 and Xq21. Subsequently, long-read sequencing and Sanger sequencing determined the inversion breakpoints at 32,915,769 and 87,989,324 of the X chromosomes. In the second pedigree, long-read sequencing was directly conducted and Sanger sequencing was performed to verify the mutation. Long-read sequencing and Sanger sequencing found breakpoints at 32,581,576 and 127,797,236 on DMD gene directly. In conclusion, large inversion might be a rare but important mutation type in DMD gene. An effective pipeline was built in detecting large inversion mutations based on long-read sequencing platforms.

Genotype-Phenotype Correlation Analysis and Identification of a Novel SRD5A2 Mutation in Four Unrelated Chinese Patients with 5α-Reductase Deficiency.

Objective: The 5α-reductase type 2 deficiency is mainly caused by mutations in the SRD5A2 gene. Our study aims to investigate the SRD5A2 gene mutations and their corresponding manifestations. Methods: Four unrelated Chinese patients with 46, XY ambiguous genitalia were studied. Molecular genetic alterations and clinical presentations were analyzed. Results: Five variants in the SRD5A2 gene were identified, all highly conserved in vertebrate orthologs. The p.P251A was a novel variant, predicted to "Affect protein function" and to be "probably damaging". Combining patients' gene mutations with their external genitalia and male sexual characteristics, we found that three variants, p.Q6X, p.N193S, and p.H90Y, were associated with severe undervirilization of external genitalia, and the other two, p.G203S and p.P251A, probably retained part of the enzyme activity. Conclusion: Mutation analysis of SRD5A2 gene is crucial for differential diagnosis in patients with 5α-reductase type 2 deficiency. Patients' variable manifestations depend on the mutation type and residual enzyme activity. The novel variant p.P251A enlarges the spectrum of SRD5A2 mutations.

Clinical characteristics and molecular etiology of partial 17α-hydroxylase deficiency diagnosed in 46,XX patients.

Introduction: Complete 17α-hydroxylase deficiency (17OHD) is relatively common, with typical juvenile female genitalia, severe hypertension, hypokalemia, and the absence of sexual development, but partial (or non-classical) 17OHD (p17OHD) is extremely rare. The p17OHD patients can present with a broad spectrum of symptoms in 46,XX karyotype including various degree of spontaneous breast development after puberty, recurrent ovarian cysts, oligomenorrhea and infertility depending on specific gene mutations and other influencing factors. Methods: This paper is a retrospective analysis of p17OHD cases from 1997 to 2021 in a Chinese tertiary hospital. Eight patients were recruited from unrelated families according to clinical data. Genotypes of patients were determined by sequencing the CYP17A1 genes. Clinical characteristics were summarized based on manifestations, hormone profiles, and responses to treatments. Results: All seven post-pubertal patients had abnormal menses. All patients had enlarged multilocular ovaries, and six (6/8) had a history of ovarian cystectomy prior to a definite diagnosis of p17OHD. All eight patients' sex hormone levels were in accord to hypogonadism with mildly elevated follicle-stimulating hormone levels, and oral contraceptives effectively suppressed the ovarian cysts. Of the four patients who underwent plasma renin activity tests, all showed results below the reference range. Fourteen alleles with a CYP17A1 mutation were found. Exon 6 was the most frequent mutation site (5/14), and four out of these five mutations were c.985_987delTACinsAA, being the most common one. In Case 2, c.1220dupA was a newly reported mutation of CYP17A1. Conclusions: 46,XX p17OHD patients were born with highly fragile ovarian reserve due to diverse mutations of CYP17A1. However, their multi-ovarian cysts can be managed conservatively for fertility preservation. This study focuses on p17OHD in 46,XX by locating the complex genetic causes in novel mutations, summarizing the puzzling spectrum of clinical manifestations, and illustrating the significance of fertility preservation in these scarce cases.

Leber congenital amaurosis as an initial manifestation in a Chinese patient with thiamine-responsive megaloblastic anemia syndrome.

Thiamine-responsive megaloblastic anemia syndrome (TRMA) is an autosomal recessive disorder, inherited by the defective SLC19A2 gene that encodes a high-affinity thiamine transporter (THTR-1). TRMA is characterized by the occurrence of classical triad manifestations including megaloblastic anemia, diabetes mellitus, and sensorineural deafness. In addition to the systemic manifestations, ophthalmic features can be present and include retinitis pigmentosa, optic atrophy, cone-rod dystrophy, maculopathy, and Leber congenital amaurosis. Here we report a 6-year-old boy presenting severe early-onset retinal dystrophy with the initial diagnosis of Leber congenital amaurosis, which followed for 12 years. Diabetes mellitus occurred 3 years after vision problem. Eosinophilic granuloma of the left scapula was confirmed at 13 years old. Whole-exome sequencing was performed to identify two novel compound heterozygous variants c.725dupC (p.Ala243Serfs*3) and c.121G>A (p.Gly41Ser) in SLC19A2 gene (NM_006996.3). Oral thiamine supplementation treatment was initiated at 13 years. This case demonstrates Leber congenital amaurosis can present as the first clinical feature before systemic manifestations. Phenotypic variety should be aware and multidisciplinary teamwork and regular follow-up are important for TRMA patient care.

A novel MAGED2 variant in a Chinese preterm newborn with transient antenatal Bartter's syndrome with 4 years follow-up.

BACKGROUND: Transient antenatal Bartter's syndrome caused by MAGED2 mutation is a rare X-linked recessive renal tubular disorder. Cases reported are mostly infants, and the long-term prognosis of the disease is still under investigation. CASE PRESENTATION: We encountered a preterm male infant with polyhydramnios, polyuria, salt loss, hypercalciuria, nephrocalcinosis and alkalosis. Antenatal Bartter's syndrome was suspected, but these clinical symptoms surprisingly disappeared after about 2 months. This led to the clinical diagnosis of transient antenatal Bartter's syndrome. Gene analysis in this patient disclosed a novel variant (c.1598C > T, p.Ala533Val) in exon 12 of MAGED2 gene, and his mother was a heterozygous carrier. This patient was followed up in clinic for 4 years without recurrence of imbalance of potassium, sodium and chloride. His height and weight were in normal range, and all laboratory examinations and nephrotic ultrasound were also normal. CONCLUSIONS: We reported the first Chinese case of transient antenatal Bartter's syndrome caused by MAGED2 mutation. The 4-year follow-up of our case further demonstrates the benign prognosis of the disease and indicates that early recognition of this phenotype could avoid unnecessary treatments.

Clinical characterization and the improved molecular diagnosis of autosomal dominant cone-rod dystrophy in patients with SCA7.

Purpose: To evaluate the retinal phenotype and genetic features of Chinese patients with spinocerebellar ataxia type 7 (SCA7). Methods: Detailed ophthalmic examinations, including electroretinograms, fundus photography, fundus autofluorescence and optical coherence tomography, were performed to analyse the retinal lesions of patients with SCA7. A molecular genetic analysis was completed to confirm the number of CAG repeats in ATXN7 gene on the patients and their family members. Results: Eight patients from three families with SCA7 were included in this study. Trinucleotide repeat was expanded from 43 to 113 in the affected patients. The affected patients were characterized by different degrees of cone-rod dystrophy, which is positively related to the number of CAG repeats and age. All patients complained of progressive bilateral visual loss, and most cases reported visual disturbance earlier than gait movement or dysarthria. A coarse granular appearance of the macular region on scanning laser ophthalmoscopy, hypofluorescence in the macula on autofluorescence, retinal atrophy on optic coherence tomography, depression of multifocal electroretinograms and prominent abnormalities in cone-mediated responses on electrograms are the general features of SCA7-related retinopathy. Hyperreflective dots in the outer retinal layers and choroidal vessel layers are a common sign in optic coherence tomography in the advanced stage. Conclusions: SCA7 shows a cone-rod dystrophy phenotype. The multimodal imaging of the retina is beneficial to detect the early lesions of cone-rod dystrophy related to SCA7.

Clinical characteristics and molecular genetics of complete androgen insensitivity syndrome patients: a series study of 30 cases from a Chinese tertiary medical center.

OBJECTIVE: To study the clinical characteristics and genetic basis of complete androgen insensitivity syndrome (CAIS) in patients from the People's Republic of China. CAIS patients with 46 XY karyotype produce male levels of androgens but present with female external genitalia and secondary sex characteristics. The majority of affected individuals have androgen receptor (AR) gene mutations. This case series explored clinical and molecular characteristics of CAIS patients from the People's Republic of China. DESIGN: Genomic DNA from peripheral blood of clinically diagnosed CAIS patients was sequenced for mutation in the androgen receptor (AR) gene and steroid 5α-reductase type 2 gene (SRD5A2). SETTING: Participants were recruited from Peking Union Medical College Hospital when they came in for consultation. PATIENTS: Thirty patients from unrelated families were recruited. INTERVENTIONS: Data from medical documents recording diagnosis and treatment of these patients were retrospectively collected. MAIN OUTCOME MEASURES: Patient genotypes were determined by sequencing the AR and SRD5A2 genes. Their clinical characteristics were summarized based on symptoms, hormone profiles, operative findings, and pathological results. RESULTS: Twenty-one patients diagnosed with CAIS had mutations in AR exons. Analysis of AR exons revealed the presence of seven novel mutations (c.58C>T, c.645_652delGGGGGCTC, c.910G>T, c.1078C>T, c.1786T>A, c.2230G>T, and c.2522G>C); of these mutations, 47.6% (10/21) were located in the ligand-binding domain. Gonadal insufficiency was found in one case of CAIS. Among the remaining nine patients, three had SRD5A2 mutations and therefore a steroid 5α-reductase deficiency. No AR or SRD5A2 mutations were detected in the other six patients. CONCLUSION: This study broadens the spectrum of known AR gene mutations responsible for CAIS, and implies that there can be more complex underlying causes of CAIS.

A Comprehensive Analysis of 2013 Dystrophinopathies in China: A Report From National Rare Disease Center.

Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are X-linked recessive neuromuscular disorders caused by mutations in DMD. A high-quality database of DMD/BMD is essential not only for clinical practice but also for fundamental research. Here, we aimed to build the largest Chinese national dystrophinopathy database using the National Rare Diseases Registry System of China. Peking Union Medical College Hospital (PUMCH) was the National Rare Diseases Center of China. This research involved 2013 patients with dystrophinopathies, whose diagnoses were confirmed; they were registered and followed up at PUMCH from March 2011 to December 2018. Family history, clinical signs, and treatment data were reported for patients with DMD and BMD at different rates. All six serum biochemical indexes could accurately distinguish between DMD and BMD patients. Copy number variations were the most frequent mutation type (79.2% in DMD and 84.3% in BMD), of which large deletions accounted for 88.4 and 88.6%, large duplications accounted for 11.6 and 11.4% in DMD and BMD, respectively. An exon deletion hotspot, located in exons 45-54, was observed in DMD, and intron 44 was the most frequent deletion starting point (26.5%). Duplication and single nucleotide variations appeared to be uniformly distributed among all exons. Eleven patients were identified to have ultrarare mutation types. Eleven other patients suffered from two separate mutations simultaneously, some of which may have taken place via dependent mechanisms. Thus, we have established the largest hospital-based Chinese dystrophinopathy database via the National Rare Diseases Registry System. This study provides valuable information for further diagnostic and therapeutic studies of dystrophinopathy.

Exonic rearrangements in DMD in Chinese Han individuals affected with Duchenne and Becker muscular dystrophies.

Exonic deletions and duplications within DMD are the main pathogenic variants in Duchenne and Becker muscular dystrophies (DMD/BMD). However, few studies have profiled the flanking sequences of breakpoints and the potential mechanism underlying the breakpoints in different fragile regions of DMD. In this study, 896 Chinese male probands afflicted with DMD/BMD were selected from unrelated families and analyzed using multiplex ligation-dependent probe amplification of the DMD gene, in which we identified exon deletions in 784 subjects and duplications in 112 subjects. Deletions occurred most frequently in the genomic region encompassing exons 45-55, accounting for 73% of all deletion patterns. Furthermore, to unravel the potential mechanism that induced breaks, DMD gene capture and sequencing were performed to identify the breakpoints in 37 subjects with deletions encompassing exons 45-55 of DMD; we found that DMD instability did not arise from a single cause; instead, long-sequence motifs, nonconsensus microhomologies, low-copy repeats, and microindels were embedded around the breakpoints, which may predispose DMD to instability. In summary, this study highlights the heterogeneous characteristics of the flanking sequences around the breakpoints and helps us to understand the mechanism underlying DMD gene instability.

Whole exome sequencing identified a novel truncation mutation in the NHS gene associated with Nance-Horan syndrome.

BACKGROUND: Nance-Horan syndrome (NHS) is an X-linked inheritance disorder characterized by bilateral congenital cataracts, and facial and dental dysmorphism. This disorder is caused by mutations in the NHS gene. However, NHS may be difficult to detect in individuals with subtle facial dysmorphism and dental abnormalities in whom congenital cataracts are the primary clinical manifestations. METHODS: In this study, we present a three-generation family with NHS. Whole exome sequencing was performed to determine the potential pathogenic variant in the proband. Further validation was explored with Sanger sequencing in 9 of the available individuals of the family and additional 200 controls. RESULTS: A novel truncation mutation in gene NHS (c.C4449G, p.Tyr1483Ter) was found in the proband, who presented with a long-narrow face, prominent nose and large anteverted pinnae ear, screw-driver like incisors, mild mulberry like molars, one missing maxillary second molar and malocclusion. We found this mutation was detected in 2 male patients and 4 female carriers in the family. However, the mutation was never detected in the control subjects. CONCLUSIONS: In conclusion, we identified a novel truncation mutation in the NHS gene, which might associate with NHS. Our review on the NHS studies illustrated that NHS has significantly clinical heterogeneity. And NHS mutations in the NHS-affected individuals typically result in premature truncation of the protein. And the new mutation revealed in this study would highlight the understanding of the causative mutations of NHS.

A heterozygous mutation in RPGR associated with X-linked retinitis pigmentosa in a patient with Turner syndrome mosaicism (45,X/46,XX).

Turner syndrome with retinitis pigmentosa (RP) is rare, with only three cases reported based on clinical examination alone. We summarized the 4-year follow-up and molecular findings in a 28-year-old patient with Turner syndrome and the typical features of short stature and neck webbing, who also had X-linked RP. Her main complaints were night blindness and progressive loss of vision since the age of 9 years. Ophthalmologic examination, optical coherent tomographic imaging, and visual electrophysiology tests showed classic manifestations of RP. The karyotype of peripheral blood showed mosaicism (45,X [72%]/46,XX[28%]). A novel heterozygous frameshift mutation (c.2403_2406delAGAG, p.T801fsX812) in the RP GTPase regulator (RPGR) gene was detected using next generation sequencing and validated by Sanger sequencing. We believe that this is the first report of X-linked RP in a patient with Turner syndrome associated with mosaicism, and an RPGR heterozygous mutation. We hypothesize that X-linked RP in this woman is not related to Turner syndrome, but may be a manifestation of the lack of a normal paternal X chromosome with intact but mutated RPGR.

Rep1 copy number variation is an important genetic cause of choroideremia in Chinese patients.

Choroidermia (CHM) is an X-linked chorioretinal disorder caused by mutations in the Rab Escort Protein 1 (Rep-1) gene. Its diagnosis depends on clinical findings and genetic confirmation; however, mutations in Rep-1 gene are not always detected by standard Sanger sequencing. We therefore conducted multiplex ligation-dependent probe amplification (MLPA) and real-time quantitative PCR (QPCR) in cases of Chinese CHM families in which sequencing all the exons and flanking intronic regions of the CHM gene had not identified a mutation or exons could not be amplified. We hypothesized that copy number variation (CNV) within the Rep-1 gene would explain the etiology of choroideremia in these patients. In the eight unrelated families, exon deletions or duplications were detected by MLPA and QPCR in five. Our results showed CNV within the Rep-1 gene could be an important contributor in Chinese CHM patients. Sequencing of the Rep-1 gene supplemented with MLPA is therefore an important diagnostic strategy in choroideremia patients.

Clinical and genetic characteristics of 17 Chinese patients with glycogen storage disease type IXa.

Glycogen storage disease (GSD) type IXa is caused by PHKA2 mutation, which accounts for about 75% of all the GSD type IX cases. Here we first summarized the clinical data and analyzed the PHKA2 gene of 17 Chinese male patients suspected of having GSD type IXa. Clinical symptoms of our patients included hepatomegaly, growth retardation, and liver dysfunction. The clinical and biochemical manifestations improved and even disappeared with age. We detected 14 mutations in 17 patients, including 8 novel mutations; exons 2 and 4 were hot spots in this research. In conclusion, glycogen storage disease type IXa is a mild disorder with a favorable prognosis, and there was no relationship between genotype and phenotype of this disease.

Mutation Analysis of 16 Mucolipidosis II and III Alpha/Beta Chinese Children Revealed Genotype-Phenotype Correlations.

Mucolipidosis II and III alpha/beta are autosomal recessive diseases caused by mutations in the GNPTAB gene which encodes the α and ß subunits of the N-acetylglucosamine-1-phosphotransferase. Clinically, mucolipidosis II (MLII) is characterized by severe developmental delay, coarse facial features, skeletal deformities, and other systemic involvement. In contrast, MLIII alpha/beta is a much milder disorder, the symptoms of which include progressive joint stiffness, short stature, and scoliosis. To study the relationship between the genotypes and phenotypes of the MLII and MLIII alpha/beta patients, we analyzed the GNPTAB gene in 16 Chinese MLII and MLIII alpha/beta patients. We collected and analyzed the patients' available clinical data and all showed clinical features typical of MLII or MLIII alpha/beta. Moreover, the activity of several lysosomal enzymes was measured in the plasma and finally the GNPTAB gene was sequenced. We detected 30 mutant alleles out of 32 alleles in our patients. These include 10 new mutations (c.99delC, c.118-1G>A, c.523_524delAAinsG, c.1212C>G, c.2213C>A, c.2345C>T, c.2356C>T, c.2455G>T, c.2821dupA, and c.3136-2A>G) and 5 previously reported mutations (c.1071G>A, c.1090C>T, c.2715+1G>A, c.2550_2554delGAAA, and c.3613C>T). The most frequent mutation was the splicing mutation c.2715+1G>A, which accounted for 28% of the mutations. The majority of the mutations reported in the Chinese patients (57%) were located on exon 13 or in its intronic flanking regions.