Background: The initiation of puberty is heralded by increasing gonadotropin-releasing hormone (GnRH) secretion from the hypothalamus. During embryonic life the GnRH neuroendocrine network develops thanks to a coordinated migration of neurons from the nasal placode to the forebrain. Our group has previously demonstrated that dysregulation in GnRH neuronal migration leads to delayed pubertal onset. Late puberty affects up to 2% of the population and is associated with adverse health outcomes. Self-limited delayed puberty (DP) most commonly segregates within families with an autosomal dominant inheritance pattern, indicating a strong genetic basis. However, the genes underlying DP remain mainly unknown.
Aims and methods: To discover novel genetic mutations in pathways regulating GnRH neuronal development in our large, accurately phenotyped cohort of patients with DP. Whole exome sequencing was performed on DNA from 160 individuals of 67 multi-generational families affected with DP. Variants returned were analysed to identify rare, potentially pathogenic variants enriched in case versus controls and with biological relevance to GnRH neuronal development pathways. The candidate gene LGR4, identified via this strategy, was investigated using an array of in silico, in vitro and in vivo techniques.
Results: We identified three rare missense variants in LGR4 in six unrelated families (17 affected individuals) and all segregated with the DP trait with the expected autosomal dominant inheritance. These variants are highly conserved and predicted to be deleterious by the main prediction software tools. Lgr4 was specifically expressed in mice olfactory epithelium and the vomeronasal organ at different embryonic stages. The LGR4 mutants showed impaired Wnt β-catenin signalling, due to defective protein expression and a shorter protein half-life. Moreover, we investigated the role of Lgr4 in a knock-out mouse model: Lgr4+/- mice had a delayed onset of puberty and fewer GnRH neurons compared to Lgr4+/+ mice, both in early embryogenesis and at the hypothalamus, whereas Lgr4-/- mice failed to enter puberty and showed a significant reduction in GnRH neurons.
Conclusions: Defects in LGR4, acting via the Wnt signalling pathway, affect GnRH neuron development in fetal life, resulting in a phenotype of self-limited DP. Our findings contribute to the ongoing exploration of genetic factors controlling pubertal timing.
27 - 29 Nov 2019
British Society for Paediatric Endocrinology and Diabetes