Dysfunctional SEMA3E signaling underlies gonadotropin-releasing hormone neuron deficiency in Kallmann syndrome
Anna Cariboni, … , Fanny Mann, Christiana Ruhrberg
Anna Cariboni, … , Fanny Mann, Christiana Ruhrberg
Published May 18, 2015
Citation Information: J Clin Invest. 2015;125(6):2413-2428. https://doi.org/10.1172/JCI78448.
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Research Article Development Endocrinology Genetics Neuroscience

Dysfunctional SEMA3E signaling underlies gonadotropin-releasing hormone neuron deficiency in Kallmann syndrome

Abstract

Individuals with an inherited deficiency in gonadotropin-releasing hormone (GnRH) have impaired sexual reproduction. Previous genetic linkage studies and sequencing of plausible gene candidates have identified mutations associated with inherited GnRH deficiency, but the small number of affected families and limited success in validating candidates have impeded genetic diagnoses for most patients. Using a combination of exome sequencing and computational modeling, we have identified a shared point mutation in semaphorin 3E (SEMA3E) in 2 brothers with Kallmann syndrome (KS), which causes inherited GnRH deficiency. Recombinant wild-type SEMA3E protected maturing GnRH neurons from cell death by triggering a plexin D1–dependent (PLXND1-dependent) activation of PI3K-mediated survival signaling. In contrast, recombinant SEMA3E carrying the KS-associated mutation did not protect GnRH neurons from death. In murine models, lack of either SEMA3E or PLXND1 increased apoptosis of GnRH neurons in the developing brain, reducing innervation of the adult median eminence by GnRH-positive neurites. GnRH neuron deficiency in male mice was accompanied by impaired testes growth, a characteristic feature of KS. Together, these results identify SEMA3E as an essential gene for GnRH neuron development, uncover a neurotrophic function for SEMA3E in the developing brain, and elucidate SEMA3E/PLXND1/PI3K signaling as a mechanism that prevents GnRH neuron deficiency.

Authors

Anna Cariboni, Valentina André, Sophie Chauvet, Daniele Cassatella, Kathryn Davidson, Alessia Caramello, Alessandro Fantin, Pierre Bouloux, Fanny Mann, Christiana Ruhrberg

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Figure 9

SEMA3E deficiency reduces GnRH neuron numbers, projection to the ME, and testes size.

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SEMA3E deficiency reduces GnRH neuron numbers, projection to the ME, and...
(A) SEMA3E in the MPOA. Adjacent coronal sections of E14.5 mouse MPOA, immunolabeled for GnRH and PLXND1 or SEMA3E; the SEMA3A single channel is shown adjacent to the triple label. Arrowheads indicate examples of PLXND1- and GnRH-positive neurons stained for SEMA3E, consistent with SEMA3E binding to PLXND1. (B–D) SEMA3E loss reduced GnRH neuron numbers. (B) Coronal sections of E14.5 MPOA were immunolabeled to identify GnRH neurons; Δ denotes neuron deficiency in mutants compared with controls; arrowheads indicate examples of GnRH neurons with a normal, elongated morphology; black arrows indicate rounded GnRH neurons in the mutants. (C) Quantitation revealed a significant reduction in GnRH neuron numbers in Sema3e mutants compared with WT littermates. n = 3; **P < 0.01 by Student’s t test. (D) Quantitation revealed a significant reduction of GnRH neuron numbers in Sema3e mutant relative to WT forebrain, but normal numbers in the nose. n = 3; **P < 0.01 by Student’s t test. (E) Loss of SEMA3E or neural PLXND1 reduced GnRH neuron projections to the ME. Coronal sections of adult hypothalamus were immunostained to identify GnRH-positive axons (green) projecting to the ME (counterstained with DAPI, blue); innervation was poor in mutants compared with that in WT (indicated by Δ). (F) Loss of SEMA3E or neural PLXND1 reduced testes size. Testes pairs from adult littermate males were photographed side by side to demonstrate the reduced size of testes in SEMA3E-null and neuron-specific PLXND1 mutants. Scale bars: 25 μm (A); 50 μm (B); 50 μm (E); 300 μm (F).