ZSWIM7 Is Associated With Human Female Meiosis and Familial Primary Ovarian Insufficiency.

BACKGROUND: Primary ovarian insufficiency (POI) affects 1% of women and is associated with significant medical consequences. A genetic cause for POI can be found in up to 30% of women, elucidating key roles for these genes in human ovary development. OBJECTIVE: We aimed to identify the genetic mechanism underlying early-onset POI in 2 sisters from a consanguineous pedigree. METHODS: Genome sequencing and variant filtering using an autosomal recessive model was performed in the 2 affected sisters and their unaffected family members. Quantitative reverse transcriptase PCR (qRT-PCR) and RNA sequencing were used to study the expression of key genes at critical stages of human fetal gonad development (Carnegie Stage 22/23, 9 weeks post conception (wpc), 11 wpc, 15/16 wpc, 19/20 wpc) and in adult tissue. RESULTS: Only 1 homozygous variant cosegregating with the POI phenotype was found: a single nucleotide substitution in zinc finger SWIM-type containing 7 (ZSWIM7), NM_001042697.2: c.173C > G; resulting in predicted loss-of-function p.(Ser58*). qRT-PCR demonstrated higher expression of ZSWIM7 in the 15/16 wpc ovary compared with testis, corresponding to peak meiosis in the fetal ovary. RNA sequencing of fetal gonad samples showed that ZSWIM7 has a similar temporal expression profile in the developing ovary to other homologous recombination genes. MAIN CONCLUSIONS: Disruption of ZSWIM7 is associated with POI in humans. ZSWIM7 is likely to be important for human homologous recombination; these findings expand the range of genes associated with POI in women.

X-linked megalocornea caused by mutations in CHRDL1 identifies an essential role for ventroptin in anterior segment development.

X-linked megalocornea (MGC1) is an ocular anterior segment disorder characterized by an increased cornea diameter and deep anterior chamber evident at birth and later onset of mosaic corneal degeneration (shagreen), arcus juvenilis, and presenile cataracts. We identified copy-number variation, frameshift, missense, splice-site and nonsense mutations in the Chordin-like 1 gene (CHRDL1) on Xq23 as the cause of the condition in seven MGC1 families. CHRDL1 encodes ventroptin, a bone morphogenic protein antagonist with a proposed role in specification of topographic retinotectal projections. Electrophysiological evaluation revealed mild generalized cone system dysfunction and, in one patient, an interhemispheric asymmetry in visual evoked potentials. We show that CHRDL1 is expressed in the developing human cornea and anterior segment in addition to the retina. We explored the impact of loss of ventroptin function on brain function and morphology in vivo. CHRDL1 is differentially expressed in the human fetal brain, and there is high expression in cerebellum and neocortex. We show that MGC1 patients have a superior cognitive ability despite a striking focal loss of myelination of white matter. Our findings reveal an unexpected requirement for ventroptin during anterior segment development and the consequences of a lack of function in the retina and brain.

Mutation in the TBCE gene is associated with hypoparathyroidism-retardation-dysmorphism syndrome featuring pituitary hormone deficiencies and hypoplasia of the anterior pituitary and the corpus callosum.

CONTEXT: Hypoparathyroidism-retardation-dysmorphism (HRD) syndrome, an autosomal recessive disorder characterized by distinct clinical, biochemical, and genetic abnormalities, is characterized by severe short stature, the etiology of which is unclear. Homozygous mutation of the tubulin cofactor E (TBCE) gene leading to loss of four amino acids (c.155-166del12; p.del 52-55) in the TBCE protein has been associated with the syndrome. AIM: The aim of the study was to describe the clinical, biochemical, and neuroradiological features of children with genetically proven HRD syndrome. METHODS: Six children from four independent Middle Eastern pedigrees with clinical features of HRD syndrome were confirmed to have the previously reported homozygous mutation in TBCE (c.155-166del12) and were investigated with magnetic resonance imaging (MRI) of the brain and standard pituitary function testing. RESULTS: Cranial MRI in all children showed severe hypoplasia of the anterior pituitary and corpus callosum, with decreased white matter bulk. Four of five children tested had subnormal GH and cortisol responses to glucagon, and plasma IGF-I concentration was low in all six children. Cortisol response to synacthen was suboptimal in one of three patients tested. Male children (n = 3) had clinical features suggestive of hypogonadotropic hypogonadism. CONCLUSION: GH insufficiency, hypocortisolemia, and abnormal cranial MRI appear to be associated with HRD syndrome and may contribute in part to the short stature. Our data support the need for longer term monitoring for evolving pituitary hormone deficiencies and raise the possibility that TBCE may play a role in development of the anterior pituitary, corpus callosum, and white matter in addition to the parathyroid glands.