Further delineation of Wiedemann-Rautenstrauch syndrome linked with POLR3A.

Wiedemann-Rautenstrauch Syndrome (WRS; MIM 264090) is an extremely rare and highly heterogeneous syndrome that is inherited in a recessive fashion. The patients have hallmark features such as prenatal and postnatal growth retardation, short stature, a progeroid appearance, hypotonia, facial dysmorphology, hypomyelination leukodystrophy, and mental impairment. Biallelic disease-causing variants in the RNA polymerase III subunit A (POLR3A) have been associated with WRS. Here, we report the first identified cases of WRS syndrome with novel phenotypes in three consanguineous families (two Omani and one Saudi) characterized by biallelic variants in POLR3A. Using whole-exome sequencing, we identified one novel homozygous missense variant (NM_007055: c.2456C>T; p. Pro819Leu) in two Omani families and one novel homozygous variant (c.1895G>T; p Cys632Phe) in Saudi family that segregates with the disease in the POLR3A gene. In silico homology modeling of wild-type and mutated proteins revealed a substantial change in the structure and stability of both proteins, demonstrating a possible effect on function. By identifying the homozygous variants in the exon 14 and 18 of the POLR3A gene, our findings will contribute to a better understanding of the phenotype-genotype relationship and molecular etiology of WRS syndrome.

Biallelic loss-of-function variants of GFRA1 cause lethal bilateral renal agenesis.

Bilateral renal agenesis belongs to a group of perinatal lethal renal diseases. To date, pathogenic variants in three genes (ITGA8, GREB1L, and FGF20) have been shown to cause renal agenesis in humans. Recently GFRA1 has been linked to a phenotype consistent with a nonsyndromic form of bilateral renal agenesis. GFRA1 encodes a member of the glial cell line-derived neurotrophic factor receptor family of proteins. The receptor on the Wolffian duct regulates ureteric bud outgrowth in developing a functional renal system. We report on four additional affected neonates from a consanguineous family who presented with a similar lethal phenotype whereby whole exome sequencing identified a homozygous deleterious sequence variant in GFRA1 (NM_005264.8:c.628G > T:p.[Gly210Ter]). The current study represents a second confirmation report on the causal association of GFRA1 pathogenic variants with lethal nonsyndromic bilateral renal agenesis in humans.

Hypoketotic hypoglycemia without neuromuscular complications in patients with SLC25A32 deficiency.

Mitochondrial flavin adenine dinucleotide (FAD) transporter deficiencies are new entities recently reported to cause a neuro-myopathic phenotype. We report three patients from two unrelated families who presented primarily with hypoketotic hypoglycemia. They all had acylcarnitine profiles suggestive of multiple acyl-CoA dehydrogenase deficiency (MADD) with negative next-generation sequencing of electron-transfer flavoprotein genes (ETFA, ETFB, and ETFDH). Whole exome sequencing revealed a homozygous c.272 G > T (p.Gly91Val) variant in exon 2 of the SLC25A32 gene. The three patients shared the same variant, and they all demonstrated similar clinical and biochemical improvement with riboflavin supplementation. To date, these are the first patients to be reported with hypoketotic hypoglycemia without the neuromuscular phenotype previously reported in patients with SLC25A32 deficiency.