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 7

Reduced GnRH neuron numbers and increased apoptosis correlate in the Plxnd1-null MPOA.

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Reduced GnRH neuron numbers and increased apoptosis correlate in the Plx...
(A and B) PLXND1 loss caused GnRH neuron loss after the forebrain. Sagittal sections of E14.5 mouse heads were immunolabeled for GnRH, revealing fewer GnRH neurons in mutant compared with WT heads (A). Dotted lines indicate the boundary between the nose and forebrain. White dotted squares indicate regions shown at higher magnification in the adjacent panels. (B) Quantitation of GnRH neuron distribution shows that GnRH neuron loss was only significant in the mutant forebrain, but not the nose (n = 3 each; **P < 0.01, Student’s t test). (C and D) PLXND1 loss caused GnRH neuron loss in the MPOA. (C) Coronal sections of E17.5 MPOA were immunolabeled for GnRH, revealing fewer GnRH neurons in the mutant mice than in the WT mice. (D) Quantitation confirmed a significant reduction of GnRH neuron numbers in PLXND1-deficient compared with WT MPOA (n = 3 each; **P < 0.01, Student’s t test). (E and F) PLXND1 loss increased apoptosis in the MPOA. (E) Adjacent coronal sections of E14.5 MPOA were immunolabeled for GnRH together with PLXND1 or activated caspase-3, revealing apoptotic cells in areas containing GnRH neurons (indicated with solid arrowheads). Higher-magnification images of areas indicated with dotted squares are shown in the adjacent panels. (F) Quantitation shows increased cell death in the MPOA of Plxnd1-null versus WT mice (n = 3 each; **P < 0.01, Student’s t test). (G) PLXND1 loss caused GnRH neuron apoptosis. Gnrh ISH of coronal sections from E14.5 MPOA followed by immunolabeling for activated caspase-3 revealed apoptotic GnRH neurons (indicated with solid arrowheads). Scale bars: 150 μm (A and E), 50 μm (C and higher-magnification images of boxed areas in E), 45 μm (G).