Ways to Improve the Diagnosis of Growth Hormone Deficiency

Developmen

Genetic findings in short Turkish children born to consanguineous parents

IntroductionThe diagnostic yield of genetic analysis in the evaluation of children with short stature depends onassociated clinical characteristics, but the additional effect of parental consanguinity has not beenwell documented.MethodsThis observational case series of 42 short children from 34 consanguineous families was collected bysix referral centres of paediatric endocrinology (inclusion criteria: short stature and parentalconsanguinity). In eighteen patients (12 families, Group 1), the clinical features suggested a specificgenetic defect in the growth hormone (GH)-insulin-like growth factor I (IGF-I) axis, and a candidategene approach was used. In others (Group 2) a hypothesis-free approach was chosen (gene panels,microarray analysis, and whole-exome sequencing), further subdivided into 11 patients with severeshort stature (height <-3.5 SDS) and microcephaly (head circumference <-3.0 SDS) (group 2a), 10patients with syndromic short stature (group 2b) and were 3 patients with nonspecific isolated GHdeficiency (group 2c).ResultsIn all 12 families from group 1, (likely) pathogenic variants were identified in GHR, IGFALS, GH1, andSTAT5B. In 9/12 families from group 2a, variants were detected in PCNT, SMARCAL1, SRCAP, WDR4and GHSR. In 5/9 families from group 2b, variants were found in TTC37, SCUBE3, NSD2, RABGAP1,and 17p13.3 microdeletions. In group 2c no genetic cause was found. Homozygous, compoundheterozygous and heterozygous variants were found in 21, 1 and 4 patients, respectively.ConclusionGenetic testing in short children from consanguineous parents has a high diagnostic yield, especiallyin cases of severe GH deficiency or insensitivity, microcephaly, and syndromic short stature

The short mRNA isoform of the immunoglobulin superfamily, member 1 gene encodes an intracellular glycoprotein

Mutations in the immunoglobulin superfamily, member 1 gene (IGSF1/Igsf1) cause an X-linked form of central hypothyroidism. The canonical form of IGSF1 is a transmembrane glycoprotein with 12 immunoglobulin (Ig) loops. The protein is co-translationally cleaved into two sub-domains. The carboxyl-terminal domain (CTD), which contains the last 7 Ig loops, is trafficked to the plasma membrane. Most pathogenic mutations in IGSF1 map to the portion of the gene encoding the CTD. IGSF1/Igsf1 encodes a variety of transcripts. A little studied, but abundant splice variant encodes a truncated form of the protein, predicted to contain the first 2 Ig loops of the full-length IGSF1. The protein (hereafter referred to as IGSF1 isoform 2 or IGSF1-2) is likely retained in most individuals with IGSF1 mutations. [...

Case Report: A Detailed Phenotypic Description of Patients and Relatives with Combined Central Hypothyroidism and Growth Hormone Deficiency Carrying IGSF1 Mutations

In recent years, variants in immunoglobulin superfamily member 1 (IGSF1) have been associated with congenital hypopituitarism. Initially, IGSF1 variants were only reported in patients with central hypothyroidism (CeH) and macroorchidism. Later on, IGSF1 variants were also reported in patients with additional endocrinopathies, sometimes without macroorchidism. We studied IGSF1 as a new candidate gene for patients with combined CeH and growth hormone deficiency (GHD). We screened 80 male and 14 female Dutch patients with combined CeH and GHD for variants in the extracellular region of IGSF1, and we report detailed biomedical and clinical data of index cases and relatives. We identified three variants in our patient cohort, of which two were novel variants of unknown significance (p.L570I and c.1765+37C>A). In conclusion, we screened 94 patients with CeH and GHD and found variants in IGSF1 of which p.L570I could be of functional relevance. We provide detailed phenotypic data of two boys with the p.C947R variant and their large family. The remarkable phenotype of some of the relatives sheds new light on the phenotypic spectrum of IGSF1 variants

Primers used for cloning and mutagenesis.

<p>Primers used for cloning and mutagenesis.</p

Murine and rat IGSF1-2 proteins are not secreted from transfected cells.

<p>HEK293 cells were transfected with expression plasmids for wild-type (WT) or glycosylation mutant (NQ) forms of murine or rat IGSF1-2, murine transthyretin (TTR), or empty vector (pcDNA4). Note, in all cases, proteins were expressed with Myc/His tags at their C-termini. Media (top two panels) and whole cell protein lysates (bottom panel) were collected and analyzed by SDS-PAGE and immunoblotting for Myc. In the middle panel, proteins in culture medium were analyzed directly. In the top panel, proteins in the media were analyzed following Ni-NTA purification and enrichment.</p

Murine and rat IGSF1-2 are glycoproteins.

<p>A) CHO cells were transfected with empty vector (pcDNA4), wild-type murine IGSF1-2-Myc/His, or murine IGSF1-2 (N43Q)-Myc/His expression vectors. Whole cell protein lysates were collected and treated with PNGaseF (P), EndoH (E), or buffer alone (-) before being subjected to SDS-PAGE and immunoblotting (IB) with a Myc antibody. Molecular weight markers (in kDa) are shown at the left. Lanes are numbered at the bottom. B) CHO cells were transfected and lysates analyzed as in panel A, with the following exception: wild-type rat IGSF1-2-Myc/His was used in place of the mutant murine expression vector. *, non-specific band.</p