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Updated: May 3, 2026

In Vivo Functional Study of Disease-associated Rare Human Variants Using Drosophila
Published on: August 20, 2019
Functional consequences of AXL sequence variants in hypogonadotropic hypogonadism
S Salian-Mehta1, M Xu, A J Knox
1Division of Endocrinology, Metabolism, and Diabetes (S.S.-M., M.X., A.J.K., M.E.W.), Division of Cardiology (D.S., M.T.), and Department of Biochemistry and Molecular Genetics (S.B., R.S.H.), University of Colorado School of Medicine, Aurora, Colorado 80045; Veterans Affairs Research Service (M.E.W.), Veterans Affairs Medical Center, Denver, Colorado 80220; and Harvard Reproductive Endocrine Science Center and the Reproductive Endocrine Unit (L.P., W.F.C.), Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts 02114.
The AXL gene is crucial for reproductive development, impacting GnRH neuron migration and function. Mutations in AXL are rare but can cause hypogonadotropic hypogonadism, affecting sexual maturation.
Area of Science:
- Reproductive biology
- Neuroendocrinology
- Genetics
Background:
- Prior studies indicated Axl/Tyro3 null mice exhibit delayed estrus and abnormal cyclicity due to impaired GnRH neuron development.
- The TAM receptor tyrosine kinase AXL plays a role in neuronal development and survival.
Purpose of the Study:
- To investigate the role of AXL in reproductive function in mice.
- To determine if AXL mutations are associated with Kallmann syndrome (KS) or normosmic idiopathic hypogonadotropic hypogonadism (nIHH).
Main Methods:
- Assessed sexual maturation in Axl null mice.
- Sequenced the AXL gene in 104 KS/nIHH patients.
- Performed functional assays on identified AXL variants.
Main Results:
- Axl null mice showed delayed first estrus and vaginal opening.
- Identified three missense AXL mutations and one intronic variant in KS/nIHH patients.
- Mutant AXL proteins (S202C, Q361P) impaired GnRH neuronal migration and receptor processing.
Conclusions:
- AXL gene variants, though rare, have functional consequences in hypogonadotropic hypogonadism.
- The study highlights the significance of the TAM family (Tyro3, Axl, Mer) in reproductive development.
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