NKX2-2 Mutation Causes Congenital Diabetes and Infantile Obesity With Paradoxical Glucose-Induced Ghrelin Secretion.

CONTEXT: NKX2-2 is a crucial transcription factor that enables specific ß-cell gene expression. Nkx2-2(-/-) mice manifest with severe neonatal diabetes and changes in ß-cell progenitor fate into ghrelin-producing cells. In humans, recessive NKX2-2 gene mutations have been recently reported as a novel etiology for neonatal diabetes, with only 3 cases known worldwide. This study describes the genetic analysis, distinctive clinical features, the therapeutic challenges, and the unique pathophysiology causing neonatal diabetes in human NKX2-2 dysfunction. CASE DESCRIPTION: An infant with very low birth weight (VLBW) and severe neonatal diabetes (NDM) presented with severe obesity and developmental delay already at age 1 year. The challenge of achieving glycemic control in a VLBW infant was unexpectedly met by a regimen of 3 daily doses of long-acting insulin analogues. Sanger sequencing of known NDM genes (such as ABCC8 and EIF2AK3) was followed by whole-exome sequencing that revealed homozygosity of a pathogenic frameshift variant, c.356delG, p.P119fs64*, in the islet cells transcription factor, NKX2-2. To elucidate the cause for the severe obesity, an oral glucose tolerance test was conducted at age 3.5 years and revealed undetectable C-peptide levels with a paradoxically unexpected 30% increase in ghrelin levels. CONCLUSION: Recessive NKX2-2 loss of function causes severe NDM associated with VLBW, childhood obesity, and developmental delay. The severe obesity phenotype is associated with postprandial paradoxical ghrelin secretion, which may be related to human ß-cell fate change to ghrelin-secreting cells, recapitulating the finding in Nkx2-2(-/-) mice islet cells.

The novel founder homozygous V225M mutation in the HSD17B3 gene causes aberrant splicing and XY-DSD.

PURPOSE: Mutations in the gene HSD17B3 encoding the 17-beta hydroxysteroid dehydrogenase 3 enzyme cause testosterone insufficiency leading to XY disorders of sex development. In this study the clinical and molecular characteristics of three patients from consanguineous families are elucidated. METHODS: We identified three patients from two unrelated families with XY DSD and a novel homozygous HSD17B3:c. 673G>A mutation. The effect of the mutation on splicing was determined in RNA extracted from the testis of one patient. RESULTS: Three patients presented at ages 0.1, 8 and 0.7 years with ambiguous genitalia and an XY Karyotype. Endocrine workup showed normal cortisol and mineralocorticoid levels with a low testosterone/androstenedione ratio. Whole-exome sequencing, carried out in the first family, revealed a homozygous novel mutation in the HSD17B3 gene: c. 673G>A, p. V225M. The same mutation was found by Sanger sequencing in the third unrelated patient. Haplotype analysis of a 4 Mb region surrounding the HSD17B3 gene on chromosome 9 revealed that the mutation resides on the same allele in all three patients. The mutation, being the first nucleic acid on exon 10, affects splicing and causes exon 10 skipping in one of our patients' testes. CONCLUSION: The novel homozygous c. 673G>A, p. V225M mutation in the 17HSDB3 gene is likely a founder mutation and causes severe XY-DSD. It changes a conserved amino acid residue, and also alters 17HSDB3 gene transcription by causing skipping of exon 10, thereby contributing to an imbalance in the relevant protein isoforms and consequently, significant decreased 17HDSB3 enzymatic activity.

Testicular differentiation factor SF-1 is required for human spleen development.

The transcription factor steroidogenic factor 1 (SF-1; also known as NR5A1) is a crucial mediator of both steroidogenic and nonsteroidogenic tissue differentiation. Mutations within SF1 underlie different disorders of sexual development (DSD), including sex reversal, spermatogenic failure, ovarian insufficiency, and adrenocortical deficiency. Here, we identified a recessive mutation within SF1 that resulted in a substitution of arginine to glutamine at codon 103 (R103Q) in a child with both severe 46,XY-DSD and asplenia. The R103Q mutation decreased SF-1 transactivation of TLX1, a transcription factor that has been shown to be essential for murine spleen development. Additionally, the SF1 R103Q mutation impaired activation of steroidogenic genes, without affecting synergistic SF-1 and sex-determining region Y (SRY) coactivation of the testis development gene SOX9. Together, our data provide evidence that SF-1 is required for spleen development in humans via transactivation of TLX1 and that mutations that only impair steroidogenesis, without altering the SF1/SRY transactivation of SOX9, can lead to 46,XY-DSD.

Euthyroid submedian free T4 and subclinical hypothyroidism may have a detrimental clinical effect in Down syndrome.

BACKGROUND: Aberrant thyroid function is highly prevalent in Down syndrome (DS). We aimed to find whether subclinical hypothyroidism (SCH) or low-normal free T4 (FT4) are associated with a detrimental clinical outcome in untreated DS patients. METHODS: 157 patients assessed at Hadassah Down Syndrome Center between 2004 and 2010 by comprehensive clinical evaluation and tests for hemoglobin, FT4 and thyroid-stimulating hormone (TSH) were subdivided into subgroups including: clinical hypothyroidism, SCH, euthyroid submedian or supramedian FT4, and alternatively for euthyroidism and TSH levels (submedian or supramedian TSH). RESULTS: Hypothyroidism was found in 21.7% and SCH in another 14.9% of the patients. Moderate/severe hypotonia were more frequent among SCH patients compared to euthyroid patients (52.6 vs. 16.4%, p = 0.002). Patient's hemoglobin levels were lower in the euthyroid submedian FT4 group compared to the euthyroid supramedian FT4 group (10.9 vs. 0% below the normal range, p = 0.001). Interestingly, FT4 levels correlated negatively with increasing age among euthyroid DS patients (Pearson's correlation coefficient = -0.324, p = 0.009). CONCLUSION: SCH and euthyroid submedian FT4 may have significant clinical sequelae, such as hypotonia and anemia. Interventional studies with L-thyroxine replacement may be indicated in these subpopulations. Our finding that FT4 levels decrease with age in DS (contrasting the general population trend) may indicate redefining the normal FT4 levels range in DS.