Generation and characterization of a Cre-inducible MAP3K1 gain-of-function model

Area of Science:

• Molecular Biology
• Developmental Biology
• Genetics

Background:

• Mitogen-activated protein kinase kinase kinase 1 (MAP3K1) is crucial for cell signaling.
• Gain-of-Function (GoF) mutations in MAP3K1 are linked to human diseases, including 46,XY disorders of sex development (DSDs).
• Limited in vivo models hinder mechanistic studies of MAP3K1 GoF mutations.

Purpose of the Study:

• To develop a physiologically relevant in vivo model for studying MAP3K1 Gain-of-Function.
• To investigate the developmental impact and molecular mechanisms of MAP3K1 overexpression.

Main Methods:

• Generation of a Cre-inducible Map3k1 transgenic mouse (Map3k1TG) with V5 and TurboID tags.
• Tamoxifen-induced Cre activation to control Map3k1 expression in vivo.
• Analysis of developmental abnormalities, sexual differentiation, and molecular signaling pathways (MAPK, WNT/β-catenin).
• TurboID proximity labeling to identify MAP3K1 interactors.

Main Results:

• Tamoxifen-induced MAP3K1 overexpression caused dose-dependent lethality and developmental defects (reduced size, digit fusion, epidermal thickening).
• Male fetuses showed impaired sexual differentiation, with reduced anogenital distance and compromised Sertoli and germ cell populations.
• MAP3K1 induction activated MAPK and WNT/β-catenin pathways, leading to β-catenin displacement.
• Proximity labeling identified cytoskeletal-associated proteins as MAP3K1 interactors, with MAP3K1 colocalizing with actin filaments and centrosomes.

Conclusions:

• The Map3k1TG mouse model provides a versatile platform for in vivo studies of MAP3K1 GoF.
• MAP3K1 overexpression significantly impacts embryonic development and sexual differentiation.
• MAP3K1 signaling influences key developmental pathways, including MAPK and WNT/β-catenin, and interacts with cytoskeletal components.