LGR4 deficiency results in delayed puberty through impaired Wnt/β-catenin signaling.

Anna Cariboni,Federica Marelli,Leo Dunkel,Morgane Leprovots,Elena Monti,Irene Hadjidemetriou,Michael J.E Sternberg,Sasha Howard ,Claudia Cabrera ,M Garcia ,Leonardo Guasti,Alessia David,Roberto Oleari,Karoliina Wehkalampi,Michael R Barnes,Marco Bonomi,Antonella Lettieri,Alessandra Mancini,Valeria Vezzoli,Gilbert Vassart

doi:10.1172/jci.insight.133434

Abstract

The initiation of puberty is driven by an upsurge in hypothalamic gonadotropin-releasing hormone (GnRH) secretion. In turn, GnRH secretion upsurge depends on the development of a complex GnRH neuroendocrine network during embryonic life. Although delayed puberty (DP) affects up to 2% of the population, is highly heritable, and is associated with adverse health outcomes, the genes underlying DP remain largely unknown. We aimed to discover regulators by whole-exome sequencing of 160 individuals of 67 multigenerational families in our large, accurately phenotyped DP cohort. LGR4 was the only gene remaining after analysis that was significantly enriched for potentially pathogenic, rare variants in 6 probands. Expression analysis identified specific Lgr4 expression at the site of GnRH neuron development. LGR4 mutant proteins showed impaired Wnt/β-catenin signaling, owing to defective protein expression, trafficking, and degradation. Mice deficient in Lgr4 had significantly delayed onset of puberty and fewer GnRH neurons compared with WT, whereas lgr4 knockdown in zebrafish embryos prevented formation and migration of GnRH neurons. Further, genetic lineage tracing showed strong Lgr4-mediated Wnt/β-catenin signaling pathway activation during GnRH neuron development. In conclusion, our results show that LGR4 deficiency impairs Wnt/β-catenin signaling with observed defects in GnRH neuron development, resulting in a DP phenotype.

Highlights

Puberty and the timing of puberty onset are dependent on an intact network of gonadotropin-releasing hormone (GnRH) neurons working together with their afferent and efferent neural and glial connections
We aimed to investigate if defects in further pathways regulating GnRH neuronal migration and development could lead to delayed puberty (DP) onset in our large, accurately phenotyped cohort of patients with DP
Whole and targeted exome sequencing of 67 informative families from our large cohort with self-limited DP identified 8 genes significantly enriched with rare, potentially pathogenic variants by whole gene burden testing of rare variants. These candidates included 4 genes demonstrated previously to be relevant to the pathogenesis of DP (IGSF10, HS6ST1, EAP1, and FTO; refs. 1, 2, 10, and 11), 3 genes that were excluded after Sanger sequencing in patients and controls (LRRIQ3, SEC24A, and ZNF560), and the candidate gene leucine-rich repeat–containing G insight.jci.org https://doi.org/10.1172/jci.insight.133434protein–coupled receptor 4 (LGR4) ( ENSG00000205213, gene identification number 107515) (Figure 1A)

Summary

Introduction

Puberty and the timing of puberty onset are dependent on an intact network of gonadotropin-releasing hormone (GnRH) neurons working together with their afferent and efferent neural and glial connections. Development of this GnRH neuroendocrine network requires a coordinated and timely migration of neurons from the vomeronasal organ (VNO) in the nose to the hypothalamus during embryonic life. LGR4 encodes a receptor for R-spondins, the activation of which potentiates the canonical Wnt signaling pathway It is involved in the development of various organs, including the eyes, liver, reproductive tract, and bone [5]. LGR4 mutations have not been shown previously to be causal in human disease

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