Etiological identification of recurrent male fatality due to a novel NSDHL gene mutation using trio whole-exome sequencing: A rare case report and literature review

Comprehensive survey of disease-causing missense mutations of the cholesterol synthesis enzyme NSDHL: Low temperature and a chemical chaperone rescue low protein expression of select mutants

Cholesterol is essential to human life. Perturbations to any of the 22 cholesterol synthesis enzymes can lead to devastating developmental diseases. Each enzyme is exquisitely regulated both transcriptionally and post-translationally, playing a critical role in providing cholesterol to cells. We examined 13 missense mutations and one deletion mutation in the cholesterol synthesis enzyme NSDHL (NAD(P) Dependent Steroid Dehydrogenase-Like), known to cause the X-linked developmental disorders CHILD (congenital hemidysplasia with ichthyosiform erythroderma and limb defects) syndrome and CK syndrome. Little is known about the effect of these missense mutations on the stability and function of NSDHL. Here we show that protein expression levels were low for all mutants, but some could be rescued by a lower temperature (30°C vs. 37°C) and/or the chemical chaperone glycerol. Additionally, heat shock proteins 70 and 90 are needed for optimal NSDHL protein expression suggesting that disease mutations in NSDHL may interfere with this interaction, perhaps during translation resulting in lower protein synthesis. Our findings that these disease-causing mutations reduce NSDHL protein expression, but some respond to lower temperature and/or the chemical chaperone glycerol, can help inform future treatments for CHILD and CK syndrome.

Contemporary uses of "lethal" or "life limiting" terminology in perinatal research

PURPOSE OF REVIEW

A life-limiting fetal diagnosis (LLD) refers to a medical condition identified during pregnancy that is expected to lead to stillbirth, preclude ex utero survival, or significantly reduce neonatal life expectancy. The terms 'lethal' or 'life-limiting' are used to prognosticate early death for various anatomic or physiologic causes, although the expected timeframe is nonspecific. The purpose of this manuscript is to review how the terms 'lethal' or 'life limiting' are used in contemporary perinatal research.

RECENT FINDINGS

Depending on the study design, 'life-limiting' is defined either prior to data analysis (such as prospective cohort studies), or after outcomes are assessed (such as case series). When 'life-limiting' is defined prior to data analysis, study-specific specific definitions may include timeframes from birth to death, probability of neonatal mortality, or a list of diagnoses based off billing codes.

SUMMARY

Professional societies have guidelines to standardize the reporting of vital statistics, including early death. While these fall short of defining LLDs comprehensively, they present an opportunity for more specific prognostication following prenatal diagnosis, which may improve research standardization to facilitate a clearer understanding of LLDs in clinical practice.

The Landscape of Point Mutations in Human Protein Coding Genes Leading to Pregnancy Loss

Pregnancy loss is the most frequent complication of a pregnancy which is devastating for affected families and poses a significant challenge for the health care system. Genetic factors are known to play an important role in the etiology of pregnancy loss; however, despite advances in diagnostics, the causes remain unexplained in more than 30% of cases. In this review, we aggregated the results of the decade-long studies into the genetic risk factors of pregnancy loss (including miscarriage, termination for fetal abnormality, and recurrent pregnancy loss) in euploid pregnancies, focusing on the spectrum of point mutations associated with these conditions. We reviewed the evolution of molecular genetics methods used for the genetic research into causes of pregnancy loss, and collected information about 270 individual genetic variants in 196 unique genes reported as genetic cause of pregnancy loss. Among these, variants in 18 genes have been reported by multiple studies, and two or more variants were reported as causing pregnancy loss for 57 genes. Further analysis of the properties of all known pregnancy loss genes showed that they correspond to broadly expressed, highly evolutionary conserved genes involved in crucial cell differentiation and developmental processes and related signaling pathways. Given the features of known genes, we made an effort to construct a list of candidate genes, variants in which may be expected to contribute to pregnancy loss. We believe that our results may be useful for prediction of pregnancy loss risk in couples, as well as for further investigation and revealing genetic etiology of pregnancy loss.

Prenatal whole exome sequencing identified two rare compound heterozygous variants in EVC2 causing Ellis-van Creveld syndrome

BACKGROUND

Pathogenic mutations in EVC or EVC2 gene can lead to Ellis-van Creveld (EvC) syndrome, which is a rare autosomal recessive skeletal dysplasia disorder. This study aimed to determine pathogenic gene variations associated with EvC syndrome in fetuses showing ultrasound anomalies.

METHODS

A 32-year-old pregnant woman from Quanzhou, China was investigated. In her pregnancy examination, the fetus exhibited multiple fetal malformations, including a narrow thorax, short limbs, postaxial polydactyly, cardiac malformations, and separation of double renal pelvis. Karyotype, chromosomal microarray analysis and whole exome sequencing were performed for prenatal genetic etiology analysis.

RESULTS

Chromosome abnormalities and copy number variants were not observed in the fetus using karyotype and chromosomal microarray analysis. Using whole exome sequencing, two compound heterozygous variants NM_147127.5:c.[2484G>A(p.Trp828Ter)];[871-2_894del] in EVC2 gene were identified in the fetus as pathogenic variants inherited from parents.

CONCLUSIONS

The study is the first to identify two rare compound variants in EVC2 gene in a Chinese family using whole exome sequencing. The application of whole-exome sequencing would be helpful in fetal etiological diagnosis with ultrasound anomalies.