Clinical and genetic features of 5 alpha-reductase type2 deficiency caused by SRD5A2 gene variants / 中华内分泌代谢杂志

Objective:To explore the clinical and genetic characteristics of 5α-reductase 2 deficiency syndrome(5α-RD2).Methods:Retrospective analysis of three cases of 5α-RD2 to summarize clinical data. Genetic testing was conducted using chromosome karyotyping analysis, whole-exome sequencing(WES), Sanger sequencing, and bioinformatics analysis. The effect of the novel variant on the structure of the 5α-reductase was evaluated by studying the homology modeling structure using SWISSMODEL and PyMoL.Results:The patients of all three cases have social gender as female. In Case 1, a 6-year-old patient sought medical attention due to abnormal external genitalia development. In Cases 2 and 3, 15-year-old patients presented with primary amenorrhea, and they showed masculinization of secondary sexual characteristics during puberty. In all three cases, the external genitalia exhibited varying degrees of masculinization, with clitoromegaly resembling a small penis and accompanying cryptorchidism. In Case 2, an hCG stimulation test was performed, and the testosterone/dihydrotestosterone(DHT) ratio was found to be 17.4. The karyotype of all three patients was 46, XY. Whole-exome sequencing(WES) detected SRD5A2 gene variants in all cases, with genotypes being p. Gln6Ter/p.Arg227Gln, p. Gln6Ter/p.Pro250Ala, and p. Arg227Ter/p.His89Tyr, respectively. Parental validation confirmed compound heterozygous mutations in all cases. The novel variant p. Pro250Ala was identified and classified as a likely pathogenic variant according to ACMG guidelines. Protein modeling analysis indicated that this variant may affect the binding of 5α-reductase 2 to NADPH. In Case 1, male gender was chosen, and a laparoscopic bilateral orchiopexy was performed. In Case 2, female gender was chosen, and testectomy and vaginoplasty were performed. The gender selection for Case 3 has not been definitively determined yet.Conclusions:Abnormal external genitalia is a common phenotype of 5α-RD2. After hCG stimulation test, there is a significant increase in the testosterone/dihydrotestosterone(DHT) ratio, which indicates that Sanger sequencing of the SRD5A2 gene can be directly performed. 5α-RD2 exhibits significant clinical heterogeneity, and WES can facilitate the differential diagnosis of 46, XY disorders of sex development. The study also reported a novel variant, p. Pro250Ala, which enriches the SRD5A2 gene variant database.

Genetic analysis of a pregnant woman with moderate intellectual disability due to variant of DLG4 gene / 中华医学遗传学杂志

OBJECTIVE@#To carry out genetic testing and prenatal diagnosis for a woman featuring moderate intellectual disability (ID).@*METHODS@#The patient had presented at the First Affiliated Hospital of Zhengzhou University on April 28, 2021. With informed consent, peripheral blood and amniotic fluid samples were collected for the extraction of genomic DNA. Pathogenic copy number variations (CNVs) were detected with CNV-seq, and single gene variants were detected by whole exome sequencing (WES) and Sanger sequencing. Candidate variant was verified by Sanger sequencing, and CNV-seq and multiplex ligation-dependent probe amplification (MLPA) were used to detect fetal CNVs.@*RESULTS@#The 23-year-old woman had moderate ID, sideway walking, and unstable holding. Ultrasonography at 18+3 weeks' gestation had revealed no fetal abnormality. No pathogenic CNV was detected in the woman by CNV-Seq, while WES revealed that she has harbored a heterozygous c.1675C>T (p.Arg559*) variant of the DLG4 gene, which was verified by Sanger sequencing. Based on guidelines from the American College of Medical Genetics and Genomics, the variant was predicted to be likely pathogenic (PVS1+PM2_supporting). Sanger sequencing has confirmed that the fetus has inherited this variant, and CNV-Seq also revealed that that fetus has harbored a 0.1 Mb heterozygous deletion at Xp21.1, which has encompassed the DMD gene, and the result was verified by MLPA.@*CONCLUSION@#The heterozygous c.1675C>T variant of the DLG4 gene probably underlay the mental retardation in this woman, and her fetus was found to harbor the same variant in addition with deletion of the DMD gene, which may predispose to ID type 62.

Analysis of a Chinese pedigree affected with Meckel syndrome due to variants of TMEM67 gene / 中华医学遗传学杂志

OBJECTIVE@#To explore the genetic etiology for a Chinese pedigree affected with Meckel syndrome.@*METHODS@#A pedigree with a history of three consecutive adverse pregnancies which presented at the First Affiliated Hospital of Zhengzhou University on August 31, 2017 was selected as the study subject. Clinical data of the pedigree were collected. High-throughput sequencing was carried out to screen for variants of ciliopathy-related genes in the third fetus following induced abortion, and candidate variant was verified by Sanger sequencing.@*RESULTS@#The first pregnancy of the couple had ended as spontaneous abortion, whilst the fetus of the second pregnancy was suspected for having ciliopathy, though no genetic testing was carried out following elected abortion. The fetus of the third pregnancy was suspected for having ciliopathy, and high-throughput sequencing and Sanger sequencing had shown that the fetus had harbored compound heterozygous variants of the TMEM67 gene, including c.978+1G>A from the father and c.1288G>C (p.D430H) from the mother. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the c.978+1G>A was classified as a pathogenic variant (PVS1+PM2_Supporting+PP5), whilst the newly discovered c.1288G>C (p.D430H) was classified as a likely pathogenic variant (PM2_Supporting+PM3+PM5+PP3).@*CONCLUSION@#The c.978+1G>A and c.1288G>C (p.D430H) compound heterozygous variants of the TMEM67 gene probably underlay the three consecutive adverse pregnancies suspected for ciliopathy in this pedigree. The discovery of c.1288G>C (p.D430H) has also expanded the mutational spectrum of the TMEM67 gene.

The value of re-sampling for patients who had failed non-invasive prenatal testing due to low cell-free fetal DNA fraction / 中华医学遗传学杂志

OBJECTIVE@#To assess the value of re-sampling for patients who had failed non-invasive prenatal testing (NIPT) due to low cell-free fetal DNA (cffDNA) fraction.@*METHODS@#Clinical data of 20 387 patients undergoing NIPT test was reviewed. The patients were re-sampled when initial blood test did not yield a result due to cffDNA fraction. The results were analyzed, and the outcome of pregnancy was followed up.@*RESULTS@#Among all samples, 17 (0.08%) had failed to yield a result due to low cffDNA fraction, all of which accepted re-sampling. A result was attained in 16 cases, with a success rate of 94.12%. Only one sample had failed the re-test.@*CONCLUSION@#For patients who had failed the initial NIPT due to low cffDNA fraction, re-sampling should be considered with gestational week and ultrasound results taken into consideration.

Non-invasive prenatal detection of ocutaneous albinism type I based on cfDNA barcode-enabled single-molecule test / 中华医学遗传学杂志

OBJECTIVE@#To assess the value of non-invasive prenatal testing based on cfDNA barcode-enabled single-molecule test (cfBEST) for the prenatal diagnosis of oculocutaneous albinism type I in a family.@*METHODS@#Prenatal genetic diagnosis was carried out by using the cfBEST-based method as well as invasive prenatal diagnosis through amniocentesis. The outcome of the pregnancy was followed up.@*RESULTS@#Non-invasive prenatal testing based on cfBEST showed a fetal DNA concentration of 6.6%, with the proportion of c.929_930insC (p.Arg311Lysfs*7) and c.1037-7T>A mutations being 45.7% and 0%, respectively. The posterior frequency of the negative results was 1, suggesting that the fetus carried neither of the two mutations. The result was consistent with that of invasive prenatal diagnosis, and the follow-up found that the fetus was normal.@*CONCLUSION@#Non-invasive prenatal testing based on cfBEST can be used to detect maternal and fetal genotypes in maternal cell-free DNA, which is clinically feasible.

Detection and analysis of dynamic variant in a pedigree affected with spinocerebellar ataxia type 3 / 中华医学遗传学杂志

OBJECTIVE@#To analyze the dynamic variant and clinical subtype of a pedigree affected with spinocerebellar ataxia (SCA) by using fluorescent-labeled primer combined with capillary electrophoresis.@*METHODS@#Genomic DNA was extracted from 8 members including 6 patients and 2 healthy individuals from the pedigree. Six pairs of fluorescent-labeled primers were designed to screen pathological variants in association with common subtypes of SCA including SCA1, SCA2, SCA3, SCA6, SCA12 and SCA17.The PCR products were detected by capillary electrophoresis.@*RESULTS@#The number of CAG repeats in the SCA3 gene of the proband were determined as 8 and 70, exceeded the normal range(12 to 40), which suggested a diagnosis of SCA3. The other five patients were all detected with abnormal CAG repeats in the SCA3 gene, while the two healthy individuals were determined to be within the normal range.@*CONCLUSION@#The abnormal expansion of CAG repeats in the SCA3 gene probably underlay the pathogenesis of the disease in this pedigree. Combined fluorescent-labeled primers PCR and capillary electrophoresis can detect dynamic variants among SCA patients with efficiency and accuracy.

Spectrum of pathological genetic variants among 405 Chinese pedigrees affected with oculocutaneous albinism / 中华医学遗传学杂志

OBJECTIVE@#To determine the spectrum of pathological genetic variants among 405 Chinese pedigrees affected with oculocutaneous albinism (OCA).@*METHODS@#A total of 405 OCA patients were collected. High-throughput sequencing (The panel included TYR, OCA2, TYRP1 and SLC45A2 genes), Sanger sequencing and multiplex ligation-dependent probe amplification (MLPA) were used to analyze the genetic variants and patterns of each subtype.@*RESULTS@#The overall detection rate of genetic variants was 79.9% (647/810), and the variants included missense variants (57.3%, 371/647), frameshift variants (22.9%, 148/647), nonsense variants (13.9%, 90/647), splicing variants (5.6%, 36/647), and microdeletions (0.3%, 2/647). Thirty-six novel variants were detected. Of the 405 patients, 306 have carried 2 variant alleles (75.6%, 306/405), 35 carried 1 variant alleles (8.6%, 35/405), while no variant was detected in 64 patients. Among the 306 genetically diagnosed OCA patients, OCA1 was the most common form (74.5%, 228/306), compared with OCA2 (15.0%, 46/306), OCA3 (0.7%, 2/306) and OCA4 (9.8%, 30/306), respectively. One patient was found to harbor homozygous c.1262-4_c.1262-3insTAGA variant of the TYRP1 gene. Another patient was found to carry compound heterozygous variants of c.1214C>A (p.T405N) and c.1338delinsCG(p.V447Gfs*19) of the TYRP1 gene.@*CONCLUSION@#High-throughput sequencing in combination with Sanger sequencing and MLPA can effectively detect genetic variants associated with OCA. Above finding has expanded variant spectrum of OCA, which can facilitate genetic and prenatal diagnosis of this disease in China.