Investigation of The Genetic Regulation of Delayed Puberty

Abstract

The genetic control of puberty remains an important but mostly unanswered question. Late pubertal timing affects over 2% of adolescents and is associated with adverse health outcomes. Self-limited delayed puberty (DP) segregates in an autosomal dominant pattern and is highly heritable; however, its neuroendocrine pathophysiology and genetic regulation remain unclear. The genetic control of puberty remains an important but mostly unanswered question. Late pubertal timing affects over 2% of adolescents and is associated with adverse health outcomes. Self-limited delayed puberty (DP) segregates in an autosomal dominant pattern and is highly heritable; however, its neuroendocrine pathophysiology and genetic regulation remain unclear. Our large, accurately phenotyped cohort of patients with familial self-limited DP is a unique resource with a relatively homogeneous genetic composition. I have utilised this cohort to investigate the genetic variants segregating with the DP trait in these pedigrees. Whole exome sequencing in eighteen probands and their relatives, and subsequent targeted sequencing in an extended subgroup of the cohort, has revealed potential novel genetic regulators of pubertal timing. In ten unrelated probands, I identified rare mutations in IGSF10, a gene that is strongly expressed in the nasal mesenchyme during embryonic migration of gonadotropin-releasing hormone (GnRH) neurons. IGSF10 knockdown both in vitro and in a transgenic zebrafish model resulted in perturbed GnRH neuronal migration. Loss-of-function mutations in IGSF10 were also identified in five patients with absent puberty due to hypogonadotropic hypogonadism (HH). Additionally, I have identified and investigated one rare, pathogenic mutation in HS6ST1 – a gene known to cause HH - in one family with DP, and two rare variants in FTO – a gene implicated in the timing of menarche in the general population - in 3 families. Further potentially pathogenic variants have emerged from investigating candidate genes identified from microarray studies (LGR4, SEMA6A and NEGR1) and from related clinical phenotypes (IGSF1). Our large, accurately phenotyped cohort of patients with familial self-limited DP is a unique resource with a relatively homogeneous genetic composition. I have utilised this cohort to investigate the genetic variants segregating with the DP trait in these pedigrees. Whole exome sequencing in eighteen probands and their relatives, and subsequent targeted sequencing in an extended subgroup of the cohort, has revealed potential novel genetic regulators of pubertal timing. In ten unrelated probands, I identified rare mutations in IGSF10, a gene that is strongly expressed in the nasal mesenchyme during embryonic migration of gonadotropin-releasing hormone (GnRH) neurons. IGSF10 knockdown both in vitro and in a transgenic zebrafish model resulted in perturbed GnRH neuronal migration. Loss-of-function mutations in IGSF10 were also identified in five patients with absent puberty due to hypogonadotropic hypogonadism (HH). Additionally, I have identified and investigated one rare, pathogenic mutation in HS6ST1 – a gene known to cause HH - in one family with DP, and two rare variants in FTO – a gene implicated in the timing of menarche in the general population - in 3 families. Further potentially pathogenic variants have emerged from investigating candidate genes identified from microarray studies (LGR4, SEMA6A and NEGR1) and from related clinical phenotypes (IGSF1).