ObjectiveResults of the screening of disease causative mutations in congenital hypothyroidism (CH) vary significantly, depending on the sequence strategy, patients’ inclusion criteria and bioinformatics. The objective was to study the molecular basis of severe congenital hypothyroidism, using the next generation sequencing (NGS) and the recent guidelines for assessment of sequence variants.Design243 patients with CH (TSH levels at neonatal screening or retesting greater than 90 mU/l) and 56 control subjects were included in the study.MethodsA custom NGS panel targeting 12 CH causative genes was used for sequencing. The sequence variants were rated according to American College of Medical Genetics and Genomics (ACMG) guidelines.ResultsIn total, 48 pathogenic, 7 likely pathogenic and 57 variants of uncertain significance were identified in 92/243 patients (37.9%), while 4 variants of uncertain significance were found in 4/56 control subjects (7.1%). 13.1% (12/92) of the cases showed variants in ‘thyroid dysgenesis’ (TD) genes: TSHR, n = 6; NKX2-1, n = 2; NKX2-5, n = 1; PAX8, n = 3. The variants in ‘dyshormonogenesis’ (DH) genes were found in 84.8% (78/92) of cases: TPO, n = 30; DUOX2, n = 24; TG, n = 8; SLC5A5, n = 3; SLC26A4, n = 6; IYD, n = 1. 8 patients showed oligonenic variants. The majority of variants identified in DH genes were monoallelic.ConclusionsIn contrast to earlier studies demonstrating the predominance of TD in severe CH, the majority of variants identified in our study were in DH genes. A large proportion of monoallelic variants detected among DH genes suggests that non-mendelian mechanisms may play a role in the development of CH.

No abstract

The next‐generation sequencing (NGS) has become a routine method for diagnostics of inherited disorders. However, assessment of the discovered variants may be challenging, especially when they are not predicted to change the protein sequence. Here we performed a functional analysis of 20 novel or rare intronic and synonymous glucokinase (GCK) gene variants identified by targeted NGS in 1,130 patients with maturity‐onset diabetes of the young. Human Splicing Finder, ver 3.1 and a precomputed index of splicing variants (SPIDEX) were used for in silico prediction. In vitro effects of GCK gene variants on splicing were tested using a minigene expression approach. In vitro effect on splicing was shown for 9 of 20 variants, including two synonymous substitutions. In silico and in vitro results matched in about 50% of cases. The results demonstrate that novel or rare apparently benign GCK gene variants should be regarded as potential splicing mutations.

Background. Gestational diabetes (GDM) due to GCK gene mutations is the most frequent form of monogenic diabetes mellitus (DM) presenting during pregnancy. It has been suggested that the use of insulin in pregnancies with fetuses carrying GCK mutations may lead to intrauterine growth retardation. In the present study we evaluated the effect of insulin therapy during pregnancy on birth weight and length in the offsprings of mothers with GDM due to GCK mutations. Aims. The aim was to study birth weight and length in offsprings of mothers with gestational diabetes mellitus due to mutations in GCK, depending on the therapy during pregnancy. Materials and methods. The study included 38 patients with GDM caused by GCK gene mutations (18.7%) and the 45 offsprings. To define molecular basis of GDM in pregnant women we used a targeted NGS. Diabetes panel genes were sequenced using a custom Ion Ampliseq gene panel and PGM semiconductor sequencer (Ion Torrent). To found the same mutations in their offsprings was used Sanger sequencing. All children were divided into 3 groups depending of their genotype and therapy received by the mothers during pregnancy. Results. We found statistically significant differences in birth length (p=0.04) and weight (p=0,031) depending on the genotype of the child and therapy in the mother. The risk of macrosomia was shown in non-mutation-carrying offsprings only. The birth weight in children with GCK gene mutations whose mothers received insulin during pregnancy was significantly lower. However, the birth weight remained in the normal range. Conclusions. Since prenatal diagnostics in the mothers with GCK gene mutations is not always justified, we recommend insulin therapy in order to prevent fetal macrosomia, which, however, should be less aggressive than in GDM due to other causes.

Congenital hypogonadotropic hypogonadism (CHH) is a rare disorder characterised by lack of pubertal development and infertility, due to deficient production, secretion or action of gonadotropin-releasing hormone (GnRH). Clinically, there are variants of CHH with hypo-/anosmia (Kalman syndrome) and normosmic hypogonadotropic hypogonadism. Given a  growing list of gene mutations accounting for CHH, the application of next generation sequencing (NGS) comprises an excellent molecular diagnostic approach because it enables the simultaneous evaluation of many genes. Biallelic mutations in GNRHR gene lead to the development of hypogonadotropic hypogonadism with normosmia. In this paper, we describe 16 patients with proven GnRH resistance and estimate the frequency of pathogenic variants in the GNRHR gene in the Russian population.