Inactivating KISS1 Mutation and Hypogonadotropic Hypogonadism

Abstract

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.

European Consensus Statement on congenital hypogonadotropic hypogonadism—pathogenesis, diagnosis and treatment

“…Some key molecules have been discovered through the study of the genetics of CHH. 1 Inactivating mutations in genes encoding kisspeptin-1 (KISS1) 40 and its receptor (KISS1R) 41,42 halt pubertal development in humans. Extensive experimental studies in various species have demonstrated that kisspeptin-producing neurons are major afferents to GnRH neurons and are essential for different aspects of GnRH function, ranging from the tonic feedback control of GnRH and/or gonadotropin secretion to generation of the pre-ovulatory surge responsible for ovulation.…”

“…21 Causative genes for Kallmann syndrome include: KAL1 (ANOS1) in the X-linked form; FGFR1 (encoding fibroblast growth factor receptor 1), 17,18 FGF8, 19,119 CHD7, [23][24][25][26][27] HS6ST1 (encoding heparan-sulphate 6-O-sulphotransferase 1), 20 SOX10, 28,29 SEMA3A (encoding semaphorin-3A), [36][37][38] WDR11 (encoding WD repeat-containing protein 11) 34,35 and IL17RD (encoding interleukin-17 receptor D) 21 in the autosomal dominant form; and PROKR2 and/or PROK2, [30][31][32][33] and FEZF1 39 in the autosomal recessive form, even though it should be noted that most patients carrying mutations in PROKR2 or PROK2 carry these mutations in the heterozygous state. 120,121 Genes involved in CHH that are associated with a normal sense of smell include GNRHR (encoding gonadotropinreleasing hormone receptor), 122,123 GNRH1 (encoding gonadotropin-releasing hormone 1), 124,125 KISS1R, 41,42 KISS1, 40,126 TACR3 and TAC3. [48][49][50] Other genes such as FGFR1 or PROKR2 can be mutated in patients with either Kallmann syndrome or CHH (Table 1).…”

Current and future applications of GnRH, kisspeptin and neurokinin B analogues

“…Substitution of Arg 9 with alanine also significantly decreased binding and activation as did substitutions of Leu 8 . Thus, Phe 6 , Arg 9 and Phe 10 appears to constitute a binding pharmacophore with proposed stacking of phenyl rings of Phe 6 and Phe 10 flanked by Arg 9 and Leu 8 with side chains orientated on the opposite side of the peptide 107 .…”

“…Inactivating mutations of two of these, kisspeptin (KP) and neurokinin B (NKB), or their cognate receptors, recently highlighted the crucial role of these neuropeptides in GnRH neurone activation, as these mutations result in a failure to progress through puberty and in adult infertility [6][7][8][9][10][11] . In addition to these major modulators of GnRH secretion, neuropeptide Y, products of the pro-opiomelanocortin protein, gonadotropin-inhibitory-hormone (GnIH) and neurotransmitters such as gamma amino butyric acid and glutamine also regulate GnRH neurone activity 12,13 .…”

“…A breakthrough in identifying such neurons occurred with the observation that inactivating mutations in genes encoding the human and mouse kisspeptin (KP) receptors (GPR54/Gpr54) resulted in a failure to progress through puberty 6,7 . An inactivating mutation in the human gene encoding KP (KiSS-1) also resulted in a failure to achieve puberty 8 .The discoveries that the KPs and their cognate receptor GPR54 play a key neuroendocrine role in the regulation of reproduction 7 is regarded as a milestone of equivalent importance to the discovery of GnRH more than three decades ago.…”