The timely secretion of gonadal sex steroids is essential for the initiation of puberty, the postpubertal maintenance of secondary sexual characteristics and the normal perinatal development of male external genitalia. Normal gonadal steroid production requires the actions of the pituitary-derived gonadotropins, luteinizing hormone and follicle-stimulating hormone. We report four human pedigrees with severe congenital gonadotropin deficiency and pubertal failure in which all affected individuals are homozygous for loss-of-function mutations in TAC3 (encoding Neurokinin B) or its receptor TACR3 (encoding NK3R). Neurokinin B, a member of the substance P-related tachykinin family, is known to be highly expressed in hypothalamic neurons that also express kisspeptin, a recently identified regulator of gonadotropin-releasing hormone secretion. These findings implicate Neurokinin B as a critical central regulator of human gonadal function and suggest new approaches to the pharmacological control of human reproduction and sex hormone-related diseases.

Keutel syndrome (KS, MIM 245150) is an autosomal recessive disorder characterized by abnormal cartilage calcification, peripheral pulmonary stenosis and midfacial hypoplasia. A genome search using homozygosity mapping provided evidence of linkage to chromosome 12p12.3-13.1 (maximum multipoint lod score, 4.06). MGP was a candidate on the basis of its localization to this chromosomal region and the known function of its protein. MGP maps to chromosome 12p near D12S363. Human MGP is a 10-kD skeletal extracellular matrix (ECM) protein that consists of an 84-aa mature protein and a 19-aa transmembrane signal peptide. It is a member of the Gla protein family, which includes osteocalcin, another skeletal ECM protein, and a number of coagulation factors (factors II, VII, IX, X and proteins S and C). All members of this family have glutamic acid residues modified to gamma-carboxyglutamic acids (Gla) by a specific gamma-carboxylase using vitamin K as a cofactor. The modified glutamic acid residues of Gla proteins confer a high affinity for mineral ions such as calcium, phosphate and hydroxyapatite crystals, the mineral components of the skeletal ECM. The pattern and tissue distribution of Mgp expression in mice suggest a role for Mgp in regulating ECM calcification. Mglap-deficient mice (Mglap-/-) have been reported to have inappropriate calcification of cartilage. Mutational analysis of MGP in three unrelated probands identified three different mutations: c.69delG, IVS1-2A-->G and c.113T-->A. All three mutations predict a non-functional MGP. Our data indicate that mutations in MGP are responsible for KS and confirm its role in the regulation of extracellular matrix calcification.

Context:Primary adrenal insufficiency (PAI) is a life-threatening condition that is often due to monogenic causes in children. Although congenital adrenal hyperplasia occurs commonly, several other important molecular causes have been reported, often with overlapping clinical and biochemical features. The relative prevalence of these conditions is not known, but making a specific diagnosis can have important implications for management.Objective:The objective of the study was to investigate the clinical and molecular genetic characteristics of a nationwide cohort of children with PAI of unknown etiology.Design:A structured questionnaire was used to evaluate clinical, biochemical, and imaging data. Genetic analysis was performed using Haloplex capture and next-generation sequencing. Patients with congenital adrenal hyperplasia, adrenoleukodystrophy, autoimmune adrenal insufficiency, or obvious syndromic PAI were excluded.Setting:The study was conducted in 19 tertiary pediatric endocrinology clinics.Patients:Ninety-five children (48 females, aged 0–18 y, eight familial) with PAI of unknown etiology participated in the study.Results:A genetic diagnosis was obtained in 77 patients (81%). The range of etiologies was as follows: MC2R (n = 25), NR0B1 (n = 12), STAR (n = 11), CYP11A1 (n = 9), MRAP (n = 9), NNT (n = 7), ABCD1 (n = 2), NR5A1 (n = 1), and AAAS (n = 1). Recurrent mutations occurred in several genes, such as c.560delT in MC2R, p.R451W in CYP11A1, and c.IVS3ds+1delG in MRAP. Several important clinical and molecular insights emerged.Conclusion:This is the largest nationwide study of the molecular genetics of childhood PAI undertaken. Achieving a molecular diagnosis in more than 80% of children has important translational impact for counseling families, presymptomatic diagnosis, personalized treatment (eg, mineralocorticoid replacement), predicting comorbidities (eg, neurological, puberty/fertility), and targeting clinical genetic testing in the future.

SUM M A R YGonadotropin-releasing hormone (GnRH) is the central regulator of gonadotropins, which stimulate gonadal function. Hypothalamic neurons that produce kisspeptin and neurokinin B stimulate GnRH release. Inactivating mutations in the genes encoding the human kisspeptin receptor (KISS1R, formerly called GPR54), neurokinin B (TAC3), and the neurokinin B receptor (TACR3) result in pubertal failure. However, human kisspeptin loss-of-function mutations have not been described, and contradictory findings have been reported in Kiss1-knockout mice. We describe an inactivating mutation in KISS1 in a large consanguineous family that results in failure of pubertal progression, indicating that functional kisspeptin is important for puberty and reproduction in humans. I t is still unknown how puberty in humans, occurring during the early years of the second decade of life, is initiated. 1 The hallmark of puberty is increased secretion of the gonadotropins, luteinizing hormone (LH) and folliclestimulating hormone (FSH), which act in concert to stimulate the gonads to drive sex-hormone secretion and gametogenesis. The production of gonadotropins from pituitary gonadotropic cells is controlled by the pulsatile delivery of GnRH. Inactivating mutations in the genes encoding GNRH1 2 or the GNRH receptor (GNRHR) 3 give rise to normosmic idiopathic hypogonadotropic hypogonadism in humans. 4 However, GnRH neurons lack sex-steroid receptors. This suggests the existence of GnRH-regulating neurons, which would mediate this effect.A major breakthrough in identifying such candidate neurons was the finding that inactivating mutations in genes encoding the human kisspeptin receptor (KISS1R, formerly called GPR54), the cognate receptor for a hypothalamic peptide, kisspeptin, resulted in pubertal failure. 4,5 More recently, mutations in TAC3 or TACR3 (encoding neurokinin B and its receptor, respectively) were shown to result in the same phenotype. 6 Kisspeptin and neurokinin B are coexpressed, along with dynorphin, in sex-hormone-responsive neurons in the arcuate nucleus (infundibular nucleus in primates), and their coordinated activity appears to regulate GnRH secretion. 7 Gene defects associated with normosmic idiopathic hypogonadotropic hypogonadism have been described in all the neuropeptides and receptors identified as stimulators of GnRH except for the kisspeptin gene (KISS1).Although Kiss1-and Kiss1r-knockout mouse models largely produce phenocopies (i.e., affected noncarriers) of human normosmic idiopathic hypogonadotropic hypogonadism resulting from inactivating mutations of KISS1R, there is evidence of remarkable residual activity of the hypothalamic-pituitary-gonadal axis.