Regulation and biological functions of MAP3K1

The National Institute of Child Health and Human Development awarded Cincinnati University of $450,811 on August 1, 2026, under the Child Health and Human Development Extramural Research program (CFDA 93.865) to investigate the regulation and biological functions of MAP3K1, a protein implicated in 46,XY disorders of sex development.

The recipient is developing and using a novel transgenic mouse model (MAP3K1TG) to define the developmental stage- and tissue-specific effects of MAP3K1 gain-of-function mutations on sexual development and fertility, and to elucidate the MAP3K1-FLNB signaling axis in regulating Wnt pathway activity and male sexual differentiation. Preliminary studies demonstrate that embryonic MAP3K1 induction reduces anogenital distance, a marker of impaired male sexual development, and activates signaling cascades known to promote female sex differentiation and repress male sex differentiation. The work includes proximity labeling proteomics to identify MAP3K1 interactions with filamin B, an actin-binding protein that regulates cytoskeletal reorganization, using genetic and signaling reporter-based approaches.

Performance occurs at Cincinnati, Ohio. The period of performance runs from August 1, 2026, through July 31, 2028. The assistance type is a Project Grant.

Abstract

Gain-of-function mutations in mitogen-activated protein kinase kinase kinase 1 (MAP3K1) have been linked to various human diseases, including 46,XY disorders of SEX development (dsds), conditions in which individuals with a male (XY) karyotype exhibit gonadal dysgenesis or female-typical phenotypes. However, a suitable in vivo model to investigate the underlying pathogenetic mechanisms is lacking. To address this GAP, we developed a novel transgenic mouse model (MAP3K1TG), in which a turboid-tagged MAP3K1 protein can be induced in a temporal and tissue-specific manner via CRE recombinase. Preliminary studies demonstrate that embryonic induction of MAP3K1 reduces anogenital distance (AGD), a robust marker indicating impaired male sexual development. In culture keratinocytes, MAP3K1 induction increases phosphorylation of mapks and activates AP-1 and WNT/β-catenin pathways, signaling cascades known to promote female SEX differentiation and repress male SEX differentiation. Moreover, proximity labeling proteomics identified MAP3K1 interactions with filamin b (flnb), an actin binding protein that regulates cytoskeletal reorganization; biochemistry analyses further validated partial colocalization of MAP3K1 with actin filaments. Intriguingly, filamin b (flnb) mutations have been implicated in 46,XY dsds and abnormal sertoli cell development through increased MAP3K1 binding and enhanced WNT pathway activation. We hypothesize that MAP3K1 gain-of-function disrupts male sexual development through aberrant interactions with flnb and dysregulation of WNT signaling. We propose two specific aims to test the hypothesis: 1) define the developmental stage- and tissue-specific effects of MAP3K1 gain-of-function on sexual development and fertility; 2) elucidate the MAP3K1-flnb signaling axis in regulating WNT pathway activity and male sexual differentiation using genetic and signaling reporter-based approaches. Dsds affect approximately 0.02% of the population, yet the genetic etiology remains undefined in most cases. Our MAP3K1TG model will provide a powerful genetic tool to elucidate disease mechanisms, leading to improved diagnostic, prognostic and patient care strategies. Moreover, this model may have broader relevance to diseases such as cancer, where MAP3K1 dysregulation also plays a pathogenic role.