A novel AVPR2 gene mutation in a Chinese pedigree with nephrogenic diabetes insipidus.

Nephrogenic diabetes insipidus (NDI) is a rare genetic disorder primarily associated with mutations in the arginine vasopressin receptor 2 (AVPR2) gene or the aquaporin 2 (AQP2) gene, resulting in impaired water reabsorption in the renal tubules. This report describes a case of a young male patient with NDI from China with a history of polydipsia and polyuria for over 15 years. Laboratory examinations of the proband indicated low urine-specific gravity and osmolality. Urologic ultrasound revealed severe bilateral hydronephrosis in both kidneys, bilateral dilatation of the ureters, roughness of the bladder wall, and the formation of muscle trabeculae. The diagnosis of diabetes insipidus was confirmed by water deprivation tests. The administration of posterior pituitary hormone did not alter urine-specific gravity, and osmolality remained at a low level (<300 mOsm/kg). Based on these findings, and the genetic tests of the proband and his parents were performed. A missense mutation (c.616 G>C) in exon 3 of the AVPR2 gene of the proband was found, caused by the substitution of amino acid valine to leucine at position 206 [p.Val206Leu], which was a hemizygous mutation and consistent with X-chromosome recessive inheritance. The administration of oral hydrochlorothiazide improves the symptoms of polydipsia and polyuria in the proband. This novel AVPR2 gene mutation may be the main cause of NDI in this family, which induces a functional defect in AVPR2, and leads to reduced tubular reabsorption of water.

Novel mutations of the X-linked genes associated with early-onset high myopia in five Chinese families.

PURPOSE: To report novel pathogenic variants of X-linked genes in five Chinese families with early-onset high myopia (eoHM) by using whole-exome sequencing and analyzing the phenotypic features. METHODS: 5 probands with X-linked recessive related eoHM were collected in Ningxia Eye Hospital from January 2021 to June 2022. The probands and their family members received comprehensive ophthalmic examinations,and DNA was abstracted from patients and family members. Whole-exome sequencing was performed on probands to screen the causative variants, and all suspected pathogenic variants were determined by Sanger sequencing and co-segregation analysis was performed on available family members. The pathogenicity of novel variants was predicted using silico analysis and evaluated according to ACMG guidelines. RT-qPCR was used to detect differences in the relative mRNAs expression of candidate gene in mRNAs available with the proband and family members in the pedigree 2. The relationship between genetic variants and clinical features was analyzed. RESULTS: All probands were male, and all pedigrees conformed to an X-linked recessive inheritance pattern. They were diagnosed with high myopia at their first visits between 4 and 7 years old. Spherical equivalent ranged between - 6.00D and - 11.00D.The five novel hemizygous variants were found in the probands, containing frameshift deletion variant c.797_801del (p.Val266Alafs*75) of OPN1LW gene in the pedigree 1, nonsense variant c.513G > A (p.Trp171Ter)of RP2 gene in the pedigree 2, missense variant c.98G > T (p.Cys33Phe) of GPR143 gene in the pedigree 3, frameshift deletion variant c.1876_1877del (p.Met626Valfs*22) of FRMD7 gene in the pedigree 4 and inframe deletion variant c.670_ 675del (p.Glu192_ Glu193del) of HMGB3 gene in the pedigree 5. All variants were classified as pathogenic or likely pathogenic by the interpretation principles of HGMD sequence variants and ACMG guidelines. In family 2, RT-qPCR showed that the mRNA expression of RP2 gene was lower in the proband than in other normal family members, indicating that such variant caused an effect on gene function at the mRNA expression level. Further clinical examination showed that pedigrees 1, 2, 3, and 4 were diagnosed as X-linked recessive hereditary eye disease with early-onset high myopia, including quiescent cone dysfunction, retinitis pigmentosa, ocular albinism, and idiopathic congenital nystagmus respectively. The pedigree 5 had eoHM in the right eye and ptosis in both eyes. CONCLUSION: In this paper,we are the first to report five novel hemizygous variants in OPN1LW, RP2, GPR143, FRMD7, HMGB3 genes are associated with eoHM. Our study extends the genotypic spectrums for eoHM and better assists ophthalmologists in assessing, diagnosing, and conducting genetic screening for eoHM.

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.

Xp21 DNA microdeletion syndrome in a Chinese family: clinical features show retinitis pigmentosa and chronic granuloma.

Xp21 DNA microdeletion syndrome is a very rare disease characterized by retinitis pigmentosa (RP), chronic granulomatous disease (CGD), and McLeod syndrome (MLS). Due to the complex and diverse clinical manifestations, early diagnosis remains a challenge for many physicians. In this study, for the purpose of determining the pathogenic gene variants and definitive diagnosis in a patient medically backgrounded with RP and CGD from a normal Chinese family, whole-exome sequencing (WES) was performed in this proband and copy number variation (CNV) was further verified in other family members by qPCR. A genetic evaluation revealed that the short arm of the X chromosome in the proband had a deletion CNV Xp21.1p11.4 (37431123-38186681) of approximately 0.755 Mb in size, and contained three contiguous OMIM genes as X-linked Kx blood group antigen (XK), cytochrome b-245 beta chain (CYBB), and RP GTPase regulator (RPGR). The qPCR results confirmed the copy number loss in Xp21.1p11.4 present in the proband and his unaffected mother. According to the American College of Medical Genetics and Genomics (ACMG) guidelines for the CNV interpretation, the deletion of this segment was a pathogenic variant. Our results provided evidence that CNV deletion of Xp21.1p11.4 in the short arm of the X chromosome was a pathogenic variant in such Chinese RP and CGD family, and the McLeod phenotype was not yet available. This study suggests that genetic testing is essential for a definitive diagnosis, which should better assist physicians in prediction, diagnosis, genetic counseling, and guidance for Xp21 DNA microdeletion syndrome.

Updated Confirmatory Diagnosis for Mucopolysaccharidoses in Taiwanese Infants and the Application of Gene Variants.

Mucopolysaccharidosis (MPS) is a lysosomal storage disease caused by genetic defects that result in deficiency of one specific enzyme activity, consequently impairing the stepwise degradation of glycosaminoglycans (GAGs). Except for MPS II, the other types of MPS have autosomal recessive inheritance in which two copies of an abnormal allele must be present in order for the disease to develop. In this study, we present the status of variant alleles and biochemistry results found in infants suspected of having MPS I, II, IVA, and VI. A total of 324 suspected infants, including 12 for MPS I, 223 for MPS II, 72 for MPS IVA, and 17 for MPS VI, who were referred for MPS confirmation from newborn screening centers in Taiwan, were enrolled. In all of these infants, one specific enzyme activity in dried blood spot filter paper was lower than the cut-off value in the first blood sample, as well asin a second follow-up sample. The confirmatory methods used in this study included Sanger sequencing, next-generation sequencing, leukocyte enzyme fluorometric assay, and GAG-derived disaccharides in urine using tandem mass spectrometry assays. The results showed that five, nine, and six infants had MPS I, II, and IVA, respectively, and all of them were asymptomatic. Thus, a laboratory diagnosis is extremely important to confirm the diagnosis of MPS. The other infants with identified nucleotide variations and reductions in leukocyte enzyme activities were categorized as being highly suspected cases requiring long-term and intensive follow-up examinations. In summary, the final confirmation of MPS depends on the most powerful biomarkers found in urine, i.e., the quantification of GAG-derived disaccharides including dermatan sulfate, heparan sulfate, and keratan sulfate, and analysis of genetic variants can help predict outcomes and guide treatment.

Becker muscular dystrophy: case report, review of the literature, and analysis of differentially expressed hub genes.

INTRODUCTION: Becker muscular dystrophy (BMD) is a genetic and progressive neuromuscular disease caused by mutations in the dystrophin gene with no available cure. A case report and comprehensive review of BMD cases aim to provide important clues for early diagnosis and implications for clinical practice. Genes and pathways identified from microarray data of muscle samples from patients with BMD help uncover the potential mechanism and provide novel therapeutic targets for dystrophin-deficient muscular dystrophies. METHODS: We describe a BMD family with a 10-year-old boy as the proband and reviewed BMD cases from PubMed. Datasets from the Gene Expression Omnibus database were downloaded and integrated with the online software. RESULTS: The systematic review revealed the clinical manifestations and mutation points of the dystrophin gene. Gene ontology analysis showed that extracellular matrix organization and extracellular structure organization with enrichment of upregulated genes coexist in three datasets. We present the first report of TUBA1A involvement in the development of BMD/Duchenne muscular dystrophy (DMD). DISCUSSION: This study provides important implications for clinical practice, uncovering the potential mechanism of the progress of BMD/DMD, and provided new therapeutic targets.

Alpha-Galactosidase A Levels in Colombian Males with End-Stage Renal Disease: Ten Years of Selective Screening in Dried Blood Spots

Abstract Fabry disease is a metabolic alteration linked to an enzymatic deficiency of Alpha-Galactosidase A, this disorder compromises the sphingolipid metabolism, leading to an accumulation of lysosomal globotriaosylceramide and is inherited in an X-linked recessive way. The diagnostic of this disease, in general, requires the confirmation of below-normal levels of Alpha-Galactosidase A obtained from dried blood spot (DBS) samples, followed by an assessment of the enzyme in leukocytes. We aimed to report the Alpha-Galactosidase A values obtained in Colombian males with end-stage renal disease (ESRD) screened using dried blood spot samples during ten years. This screening was performed with samples sent to the analysis center from 6156 patients between 2006- 2016. All patients with low levels in enzyme activity (compared to the control population) were sent to confirmation through enzyme analysis in isolated leukocytes. 26 males (0.42%) with low levels of Alpha-Galactosidase A were identified (Range 0.0 - 1.14 nmol/ml/hour, cut-off: 1.15), 22 patients were subsequently measured in isolated leukocytes having a confirmation of Fabry disease in 5 patients (0.08% of total male population) (Range: 0.3 -4.7 nmol/mg prot/h). These results are similar to those reported in studies with comparable characteristics being this the first reporting frequency of Fabry disease among Colombian males with end-stage renal disease.

Case Report: A Case of Congenital Nephrogenic Diabetes Insipidus Caused by Thr273Met Mutation in Arginine Vasopressin Receptor 2.

Congenital nephrogenic diabetes insipidus (CNDI) is a rare hereditary tubular dysfunction caused mainly by X-linked recessive inheritance of AVPR2 gene mutations. Pathogenic genes are a result of mutations in AVPR2 on chromosome Xq28 and in AQP2 on chromosome 12q13. The clinical manifestations of CNDI include polyuria, compensatory polydipsia, thirst, irritability, constipation, developmental delay, mental retardation, persistent decrease in the specific gravity of urine, dehydration, and electrolyte disorders (hypernatremia and hyperchloremia). Herein, we report a rare case of CNDI caused by an AVPR2 mutation in a 2-year-old Chinese boy who had sustained polyuria, polydipsia, and irritability for more than 20 months. Laboratory examinations showed no obvious abnormality in blood sodium and chloride levels but decreased urine osmolality and specific gravity. Imaging findings were also normal. However, genetic analysis revealed a C > T transition leading to T273M missense mutations in AVPR2. We provided the boy a low-sodium diet and administered oral hydrochlorothiazide and indomethacin for 1 month, after which his clinical symptoms significantly improved. This case report suggests that CNDI is characterized by pathogenic T273M missense mutations alone and expands our understanding of the pathogenesis of CNDI.

Prenatal Genetic Testing for X-Linked Hypohidrotic Ectodermal Dysplasia.

INTRODUCTION: Hypohidrotic ectodermal dysplasia (HED) is an X-linked recessive disorder, characterised by abnormally developed ectodermal tissues (sweat glands, enamel, hair, nails). HED is caused by mutations of the EDA1 gene (Xq13.1) which codes for ectodysplasin A, a transmembrane signalling protein, which plays a significant role in ectodermal differentiation. Here we present a case of prenatal testing for HED. METHODS: An 11-month-old boy with no family history was clinically diagnosed with HED. Genomic DNA was isolated from the patient's white blood cells, and the possible existence of mutations suspected for HED development was investigated by an NGS gene panel. Total DNA was also isolated from blood samples of his parents. After mutation detection and genetic counselling, a prenatal HED test was performed during the 12th week of the mother's next pregnancy. Embryonic DNA was isolated from a sample of chorionic villi. Parts of the EDA1, AMELX (X chromosome), and SRY (Y chromosome) genes were amplified by PCR, using the corresponding primers. RESULTS: The boy with HED was found to be a hemizygote for the c.595_613del (p. Pro199PhefsTer75) deletion in the EDA1 gene. The fetus was male (XY) that did not carry the pathological mutation. CONCLUSION: The initial diagnosis of a family member with HED in a case with no family history poses the question whether this type of ectodermal dysplasia is autosomal dominant (and the case is due to a de novo mutation), autosomal recessive, or X-linked recessive. Molecular detection of the responsible mutation allows proper genetic counselling, carrier testing, and prevention by prenatal testing.

Non-syndromic anophthalmia/microphthalmia can be caused by a PORCN variant inherited in X-linked recessive manner.

Anophthalmia and microphthalmia (A/M) represent severe developmental ocular malformations, corresponding, respectively, to absent eyeball or reduced size of the eye. Both anophthalmia and microphthalmia may occur in isolation or as part of a syndrome. Genetic heterogeneity has been demonstrated, and many genes have been reported to be associated with A/M. The advances in high-throughput sequencing have proven highly effective in defining the molecular basis of A/M. Nevertheless, there are still many patients with unsolved genetic background of the disease, who pose a significant challenge in the molecular diagnostics of A/M. Here we describe a family, with three males affected with the non-syndromic A/M. Whole exome-sequencing performed in Patient 1, revealed the presence of a novel probably pathogenic variant c.734A>G, (p.[Tyr245Cys]) in the PORCN gene. Pedigree analysis and segregation of the identified variant in the family confirmed the X-linked recessive pattern of inheritance. This is the first report of X-linked recessive non-syndromic A/M. Until now, pathogenic variants in the PORCN gene have been identified in the patients with Goltz syndrome, but they were inherited in X-linked dominant mode. The ocular phenotype is the only finding observed in the patients, which allows to exclude the diagnosis of Goltz syndrome.

A novel GPR143 mutation in a Chinese family with X­linked ocular albinism type 1.

Ocular albinism type 1 (OA1) is a genetic disorder characterized by reduced eye pigmentation and nystagmus, which is often accompanied by decreased visual acuity, strabismus and other symptoms, whereas skin and hair color remain normal. The present study aimed to assess the clinical features and perform genotype analysis of a family with OA1, and to determine the disease­causing mutation. A total of 18 family members (nine affected patients and nine normal subjects) from Hainan, China, were recruited to the present study in December 2017. A detailed clinical ophthalmic examination was performed for all participants, including a visual acuity test, anterior segment slit lamp examination, eye fundus examination and optical coherence tomography. Mutations in the G protein­coupled receptor 143 (GPR143) gene were determined by DNA sequencing assays and polymerase chain reaction assays for deletions; all exon coding sequences, exons at the 5'­ and 3'­ends, and non­coding region sequences of intron splicing were assessed. Within the family, nine male patients exhibited disease occurrence at the age of 0­6 months. All patients presented with different degrees of iris depigmentation, horizontal jerk nystagmus, foveal hypoplasia and reduced visual acuity. The fundus of only one patient exhibited choroid coloboma; in the remaining patients, their fundi exhibited different degrees of irregular retinal depigmentation. The mutation c.360+5G>T in the GPR143 gene was identified in this family. In conclusion, the present study identified the splicing mutation c.360+5G>T in the GPR143 gene in a Chinese family with OA1 and successfully identified the site. To the best of our knowledge, there have been no previous reports regarding this mutation in any major genome databases; therefore, this outcome may enrich the mutation spectrum of the GPR143 gene.

Photoreceptor degeneration in a new Cacna1f mutant mouse model.

The Cacna1f gene encodes the α1F subunit of an L-type voltage-gated calcium channel, Cav1.4. In photoreceptor synaptic terminals, Cav1.4 channels mediate glutamate release and postsynaptic responses associated with visual signal transmission. We have discovered a new Cacna1f mutation in nob9 mice, which display more severe phenotypes than do nob2 mice. To characterize the nob9 phenotype at different ages, we examined the murine fundus, applied retinal optical coherence tomography, measured flash electroretinograms (ERGs) in vivo, and analyzed the retinal histology in vitro. After identifying the X-linked recessive inheritance trait, we sequenced Cacna1f as the candidate gene. Mutations in this gene were detected by polymerase chain reaction (PCR) and confirmed by restriction fragment length polymorphism. Morphologically, an early-onset of retinal disorder was detected, and the degeneration of the outer plexiform layers progressed rapidly. Moreover, the mutant mice showed drastically reduced scotopic ERGs with increasing age. In 14-month-old nob9 retinas, immunostaining of cone opsins demonstrated a reduction in the number of short-wavelength opsins (S-opsins) to 54% of wild-type levels, and almost no middle-wavelength opsins (M-opsins) were observed. No cone ERGs could be detected from residual cones, in which S-opsins abnormally migrated to inner segments of the photoreceptors. The mutations of the Cacna1f gene in nob9 mice involved both a single nucleotide G to A transition and a 10-nucleotide insertion, the latter resulting in a frame-shift mutation in exon 14.

Prevalence of Fabry disease in dialysis patients: Japan Fabry disease screening study (J-FAST).

BACKGROUND: In Fabry disease, progressive glycolipid accumulation leads to damage in kidney and other organs. This study was designed to determine the prevalence rate of Fabry disease in Japanese dialysis patients. METHODS: All dialysis patients agreeing to Japan Fabry disease screening study (J-FAST) with informed consent were selected except for Fabry disease. The screening was performed by a method of measuring plasma and/or leukocytes lysosomal α-galactosidase A protein level and α-galactosidase A activity. If positive, genetic analysis was carried out upon patient's agreement. RESULTS: J-FAST dealt with 8547 patients (male 5408, female 3139). At the tertiary examination, 26 out of 8547 patients were found to be positive. Six out of 26 patients could not accept genetic analysis because of death. Remaining 20 patients agreed with genetic analysis; then 2 patients (male 2, female 0) had a variation of the α-Gal gene and 11 patients showed E66Q variations. Therefore, the frequency of Fabry disease in J-FAST was 0.04 % (2/5408) in males and 0 % (0/3139) in females, and then 0.02 % (2/8547) in all patients. The presumptive clinical diagnoses of end-stage kidney disease (ESKD) were 10 chronic glomerulonephritis, 7 diabetic nephropathy, 3 unknown etiology, 3 nephrosclerosis, 1 gouty nephropathy, 1 autosomal dominant polycystic kidney disease and 1 renal tuberculosis among 26 tertiary positive patients. Two male Fabry patients were initially diagnosed as nephrosclerosis and chronic glomerulonephritis. CONCLUSIONS: The prevalence rate of Fabry disease in J-FAST was 0.02 %. Moreover, Fabry disease could not be ruled out as the clinical diagnosis of ESKD.

An unusual phenotype of X-linked developmental delay and extreme behavioral difficulties associated with a mutation in the EBP gene.

We report on a family in which four males over three generations are affected with X-linked recessive developmental delay, learning difficulties, severe behavioral difficulties and mild dysmorphic features. Plasma sterol analysis in three of the four affected males demonstrated increased concentrations of 8-dehydrocholesterol (8-DHC) and cholest-8(9)-enol. All four affected males had a novel hemizygous missense mutation, p.W47R (c.139T>C), in EBP. Functional studies showed raised levels of cholest-8(9)-enol in patient's cultured fibroblast cells, which were suppressed when the cells were incubated with simvastatin. EBP encodes 3ß-hydroxysteroid-delta8, delta7-isomerase, a key enzyme involved in the cholesterol biosynthesis pathway. Mutations in EBP have previously been associated with Conradi-Hunermann-Happle syndrome (CHH), an X-linked dominant disorder characterized by skeletal dysplasia, skin, and ocular abnormalities, which is usually lethal in males. Four previous reports describe X-linked recessive multiple anomaly syndromes associated with non-mosaic EBP mutations in males, two at the same amino acid position, p.W47C. This phenotype has previously been described as "MEND" syndrome (male EBP disorder with neurological defects). The family reported herein represent either a novel phenotype, or an expansion of the MEND phenotype, characterized by extreme behavioral difficulties and a scarcity of structural anomalies. Simvastatin therapy is being evaluated in two males from this family.

Guía clínica: consenso para Chile en enfermedad de Fabry / Clinical guidelines: Chilean consensus in Fabry disease

Fabry's disease is an X-linked recessive inborn error of metabolism of glycosphingolipids, caused by the deficiency of the lisosomal enzyme alpha-galactosidase. It is a rare disease with an estimated incidence rate of approximately 1:80.000 to 1:117,000 births in the general population. Recently, the growing knowledge about this disease has permitted the development of enzyme replacement therapy, which has modified the prognosis and quality of life of these patients. In Chile, the real incidence is unknown, but the increase in the number of patients diagnosed during the last five years, mainly in the north of the country. This guide was prepared with the intention of establishing a consensus for the diagnosis, treatment and monitoring of the patients with Fabry disease based on the present available scientific evidence.

La enfermedad de Fabry es un error innato del catabolismo de los glucoesfingolipidos, de herencia recesiva ligada al cromosoma X, causado por la deficiencia de la enzima lisosomal alfa-galactosidasa A (alfa-gal A). Es un defecto poco frecuente, con una incidencia estimada de 1:80.000 a 1:117.000, entre la población general. Recientemente, el creciente conocimiento acerca de esta enfermedad, ha permitido el desarrollo de la terapia de reemplazo enzimático, la cual ha modificado el pronóstico y calidad de vida de los pacientes. En Chile, se desconoce la incidencia real, pero el aumento del número de pacientes diagnosticados durante los últimos cinco años, principalmente en la zona norte del país, ha generado un mayor interés por esta enfermedad. Esta guía fue elaborada con la intención de establecer un consenso para el diagnóstico, tratamiento y seguimiento de los pacientes con enfermedad de Fabry, basado en la evidencia científica, actualmente disponible.