Transcriptomic Analysis of MAP3K1 and MAP3K4 in the Developing Marsupial Gonad.

Area of Science:

• * Developmental Biology
• * Genetics
• * Comparative Genomics

Background:

• * Mitogen-activated protein kinase (MAPK) pathways are crucial for gonadal differentiation in eutherian mammals like mice and humans.
• * The role of MAPKs in gonadal development across all mammalian groups, particularly marsupials, remains largely unexplored.
• * Oestrogen is known to induce gonadal sex reversal, providing a model to study sex determination pathways.

Purpose of the Study:

• * To investigate MAPK gene expression during gonadal differentiation in the marsupial tammar wallaby.
• * To determine the effect of oestrogen treatment on MAPK expression and gonadal development in this species.
• * To compare MAPK gene conservation and identify potential marsupial-specific variations.

Main Methods:

• * High-throughput RNA-sequencing (RNA-seq) of tammar wallaby gonads from prenatal to postnatal stages.
• * In vitro culture of day 25 fetal testes with and without exogenous oestrogen, followed by RNA-seq.
• * Bioinformatic analysis of MAPK pathway genes and key sexual differentiation markers (SOX9, AMH, FOXL2).

Main Results:

• * MAPK pathway genes in tammar wallabies show high sequence and amino acid conservation with mice and humans.
• * Marsupial MAP3K1 and MAP3K4 genes form a distinct evolutionary branch separate from eutherian mammals.
• * Oestrogen treatment of male tammar gonads decreased SOX9 and AMH expression while increasing FOXL2; only MAP3K1 expression was upregulated.

Conclusions:

• * The MAPK pathway is conserved in marsupials, but specific genes like MAP3K1 and MAP3K4 exhibit unique evolutionary trajectories.
• * Exogenous oestrogen influences key sex-determining gene expression in developing male tammar wallaby gonads.
• * MAP3K1 is identified as a potential mediator of oestrogen's effects during gonadal differentiation in this marsupial model.