Sex-specific transcriptome dynamics of Anopheles gambiae during embryonic development

Area of Science:

• Genomics
• Developmental Biology
• Entomology

Background:

• Mosquitoes exhibit significant sexual dimorphism, but the origins of sex-specific gene expression during embryogenesis are poorly understood.
• While adult sex-specific gene expression is known, early embryonic stages, excluding sex determination factors, remain largely uncharacterized.

Purpose of the Study:

• To create a comprehensive single-embryo transcriptome atlas for male and female *Anopheles gambiae* embryos.
• To investigate the earliest stages of sex-specific expression network establishment during mosquito embryogenesis.

Main Methods:

• Single-embryo RNA sequencing of *Anopheles gambiae* males and females.
• Analysis of embryonic RNA isoform diversity, alternative polyadenylation (APA), sex-biased gene expression, and alternative splicing.
• Investigation of X-chromosome dosage compensation (DC) establishment and its master regulator, SOA.

Main Results:

• Identified widespread embryonic RNA isoform diversity, including a shift towards distal APA during the maternal-to-zygotic transition.
• Observed limited sex-biased gene expression and alternative splicing during embryogenesis, with most patterns appearing postembryonically.
• Found X-chromosome dosage compensation (DC) is established early, with SOA binding dynamically specified based on gene activity, not fixed high-affinity sites.

Conclusions:

• Most sex-specific gene expression and alternative splicing patterns in *Anopheles gambiae* emerge after embryogenesis.
• The *Anopheles* dosage compensation system is a dynamic, gene-by-gene regulatory mechanism operating at the chromosome-wide level.
• SOA binding and DC are closely linked to gene activity levels, representing an extreme form of gene-by-gene regulation.