Y chromosome damage underlies testicular abnormalities in ATR-X syndrome.

ATR-X (alpha thalassemia, mental retardation, X-linked) syndrome features genital and testicular abnormalities including atypical genitalia and small testes with few seminiferous tubules. Our mouse model recapitulated the testicular defects when Atrx was deleted in Sertoli cells (ScAtrxKO) which displayed G2/M arrest and apoptosis. Here, we investigated the mechanisms underlying these defects. In control mice, Sertoli cells contain a single novel "GATA4 PML nuclear body (NB)" that contained the transcription factor GATA4, ATRX, DAXX, HP1α, and PH3 and co-localized with the Y chromosome short arm (Yp). ScAtrxKO mice contain single giant GATA4 PML-NBs with frequent DNA double-strand breaks (DSBs) in G2/M-arrested apoptotic Sertoli cells. HP1α and PH3 were absent from giant GATA4 PML-NBs indicating a failure in heterochromatin formation and chromosome condensation. Our data suggest that ATRX protects a Yp region from DNA damage, thereby preventing Sertoli cell death. We discuss Y chromosome damage/decondensation as a mechanism for testicular failure.

MFSD7c functions as a transporter of choline at the blood-brain barrier.

Mutations in the orphan transporter MFSD7c (also known as Flvcr2), are linked to Fowler syndrome. Here, we used Mfsd7c knockout (Mfsd7c-/-) mice and cell-based assays to reveal that MFSD7c is a choline transporter at the blood-brain barrier (BBB). We performed comprehensive metabolomics analysis and detected differential changes of metabolites in the brains and livers of Mfsd7c-/-embryos. Particularly, we found that choline-related metabolites were altered in the brains but not in the livers of Mfsd7c-/- embryos. Thus, we hypothesized that MFSD7c regulates the level of choline in the brain. Indeed, expression of human MFSD7c in cells significantly increased choline uptake. Interestingly, we showed that choline uptake by MFSD7c is greatly increased by choline-metabolizing enzymes, leading us to demonstrate that MFSD7c is a facilitative transporter of choline. Furthermore, single-cell patch clamp analysis showed that the import of choline by MFSD7c is electrogenic. Choline transport function of MFSD7c was shown to be conserved in vertebrates, but not in yeasts. We demonstrated that human MFSD7c is a functional ortholog of HNM1, the yeast choline importer. We also showed that several missense mutations identified in patients exhibiting Fowler syndrome had abolished or reduced choline transport activity. Mice lacking Mfsd7c in endothelial cells of the central nervous system suppressed the import of exogenous choline from blood but unexpectedly had increased choline levels in the brain. Stable-isotope tracing study revealed that MFSD7c was required for exporting choline derived from lysophosphatidylcholine in the brain. Collectively, our work identifies MFSD7c as a choline exporter at the BBB and provides a foundation for future work to reveal the disease mechanisms of Fowler syndrome.

An extremely rare missense mutation of the androgen receptor gene in a Vietnamese family with complete androgen insensitivity syndrome.

We report a Vietnamese family with complete androgen insensitivity syndrome that included several phenotypic females who have a 46,XY karyotype with an extremely rare mutation of the androgen receptor gene. The proband was a 27-year-old phenotypic adult female referred to our department for karyotyping due to primary amenorrhea. Ultrasound examination revealed a small uterus. Chromosomal analysis showed a 46,XY karyotype. A polymerase chain reaction assay revealed the presence of the sex-determining region Y gene. Next-generation sequencing detected the NM_000044.6(AR):c.2170C>T(p.Pro274Ser) mutation, which was confirmed by Sanger sequencing. There is only one previous report of this mutation in a child with complete androgen insensitivity syndrome. In the family presented in this study, there were four more phenotypic adult females with primary amenorrhea and a phenotypic female infant with testes in the inguinal canals. The infant (first cousin once removed of the proband) presented with inguinal hernia/swelling in a phenotypic female and one of the four abovementioned adults had similar genetic analysis results. This is the second report of a missense mutation NM 000044.6(AR):c.2170C>T in the world and the first study to document a pedigree consisting of several individuals with CAIS as a result of this mutation. The presence of a tiny uterus in the proband, which is a rare occurrence in complete androgen insensitivity syndrome, is a unique clinical indicator of the disorder's variable expressivity.

Mfsd2b and Spns2 are essential for maintenance of blood vessels during development and in anaphylactic shock.

Sphingosine-1-phosphate (S1P) is a potent lipid mediator that is secreted by several cell types. We recently showed that Mfsd2b is an S1P transporter from hematopoietic cells that contributes approximately 50% plasma S1P. Here we report the characterization of compound deletion of Mfsd2b and Spns2, another S1P transporter active primarily in endothelial cells. Global deletion of Mfsd2b and Spns2 (global double knockout [gDKO]) results in embryonic lethality beyond embryonic day 14.5 (E14.5), with severe hemorrhage accompanied by defects of tight junction proteins, indicating that Mfsd2b and Spns2 provide S1P for signaling, which is essential for blood vessel integrity. Compound postnatal deletion of Mfsd2b and Spns2 using Mx1Cre (ctDKO-Mx1Cre) results in maximal 80% reduction of plasma S1P. ctDKO-Mx1Cre mice exhibit severe susceptibility to anaphylaxis, indicating that S1P from Mfsd2b and Spns2 is indispensable for vascular homeostasis. Our results show that S1P export from Mfsd2b and Spns2 is essential for developing and mature vasculature.

An Extremely Rare SRD5A2 Gene c.485A>C Mutation in a Compound Heterozygous Newborn with Disorders of Sex Development First Identified in Vietnam.

SRD5A2 (steroid 5-alpha-reductase 2) mutation, which impairs 5α-reductase-2 enzyme activity, is among the causes of 46,XY disorders of sex development (DSD). Here, we report a rare pathogenic mutation NM_000348.4:c.485A>C (NP_000339.2:p.His162Pro) of SRD5A2 gene in a compound heterozygous state first identified in a Vietnamese newborn with 5α-reductase-2 enzyme deficiency. We also first submitted this rare mutation to ClinVar database (VCV000973099.1). The patient presented with hyperpigmented labia-majora-like bifid scrotum, clitoris-like phallus, perineoscrotal hypospadias, and blind-ending vagina. The other mutation NM_000348.4:c.680G>A (NP_000339.2:p.Arg227Gln) was reported previously. This compound heterozygous mutation was first detected by next-generation sequencing. By Sanger sequencing, we confirmed that the c.485A>C mutation was maternal inherited, whereas the c.680G>A mutation was paternal inherited. Up to date, this is the first report of this rare compound heterozygous state of SRD5A2 c.485A>C and c.680G>A mutations in patients with 46,XY DSD generally as well as in Vietnamese population particularly and is also the second report in the world carrying the pathogenic mutation NM_000348.4:c.485A>C (NP_000339.2:p.His162Pro). Our finding has enriched the understanding of the spectrum of SRD5A2 variants and phenotypic correlation in Asian patients with 46,XY DSD.

MBD5-related intellectual disability in a Vietnamese child.

The disruption of methyl-binding domain protein 5 (MBD5) gene has been determined as a significant cause of a group of disorders known as MBD5-associated neurodevelopmental disorder. Here, we report a novel pathogenic mutation, NM_001378120.1 (MBD5): c.217-1G>C, occurring at the acceptor splicing site of intron 6 of the MBD5 gene identified in a Vietnamese child with intellectual disability, autistic-like behaviors, and seizure. Phenotypic manifestations in this patient are highlighted with neurodevelopmental impairments whereas his facial dysmorphism is unremarkable. Our finding has enriched the understanding of the spectrum of MBD5 variants, a critical database for diagnosis, genetic counseling, and management of the patients with neurological diseases.

An experience in prenatal diagnosis via QF-PCR of a female child with a 9.9 Mb pure deletion at 18p11.32-11.22.

Quantitative Fluorescent - Polymerase Chain Reaction (QF-PCR) is a rapid prenatal diagnosis test for 21, 18, 13 and sex chromosomal aneuploidy detection. However, it could not detect partial trisomy or partial monosomy of those chromosomes. Here, we report a 19-month-old Vietnamese female with a 9.9 Mb pure deletion of chromosome 18 at 18p11.32-11.22 confirmed by next generation sequencing. The patient was short statured with facial dysmorphic features as well as motor skill and speech delays. First trimester screening showed high risk of trisomy 21 with only increased nuchal translucency (NT 3.9 mm) by ultrasound as an indication. Prenatal diagnosis by QF-PCR from amniotic DNA revealed normal disomy. Noticeably, two short tandem repeat (STR) markers D18S391 and D18S976 located on 18p exhibited uninformative patterns (one peak). Thus, our case suggested that the combination of both D18S391 and D18S976 markers with uninformative patterns in QF-PCR for prenatal diagnosis and increased NT in the first trimester ultrasound may be a significant indication of 18p monosomy.

Association of TP53 gene codon 72 polymorphism with Helicobacter pylori-positive non-cardia gastric cancer in Vietnam.

INTRODUCTION: This research aimed to determine the association of the combination of H. pylori infection and TP53 codon 72 polymorphism with non-cardia gastric cancer (GC) in Vietnam. METHODOLOGY: A total of 164 patients with non-cardia GC and 164 patients with peptic ulcer disease or functional dyspepsia in controls matched by sex and age were enrolled. H. pylori infection was diagnosed by rapid urease test and polymerase chain reaction (PCR). The cagA gene-positivity and vacA sm subtypes were determined by multiplex PCR. Genotypes of TP53 codon 72 polymorphism were determined by PCR-restriction fragment length polymorphism. RESULTS: The prevalence of H. pylori infection in GC and control group were 61.6% and 55.4%, respectively. The rates of cagA-positive strains in the two H. pylori-positive groups were 80.2% and 71.4%, respectively. There was no statistically significant difference in TP53 codon 72 genotype distribution between GC group (frequencies of Arg/Arg, Arg/Pro and Pro/Pro genotypes were 31.1%, 43.3% and 25.6%, respectively) and controls (29.3%, 52.4% and 18.3%, respectively), p = 0.172. The significant difference in genotype distribution was observed in recessive model (Pro/Pro vs Arg/Arg + Arg/Pro) when stratifying by H. pylori infection (OR = 2.02, 95% CI 1.03-3.96, p = 0.041) and by cagA-positivity (OR = 2.33, 95% CI 1.07-5.07, p = 0.032). CONCLUSIONS: This study suggests a synergistic interaction between H. pylori infection, especially cagA-positive H. pylori, and Pro/Pro genotype of TP53 codon 72 polymorphism might play a significant role in the pathogenesis of GC in the Vietnamese population.