Cell type specific allometry controls sex-differences in Drosophila organ size.

Area of Science:

• Developmental biology
• Comparative genomics
• Cellular and molecular biology

Background:

• Sex-specific differences in organ size are common in animals but poorly understood.
• In Drosophila, adult females are larger than males, but the cellular mechanisms driving this size difference are unclear.

Purpose of the Study:

• To investigate the cellular and molecular mechanisms underlying sex-specific organ and body size scaling in Drosophila.
• To determine if organ scaling occurs uniformly or through distinct strategies involving cell size and/or cell number.

Main Methods:

• Analysis of single-nucleus transcriptomes from the Fly Cell Atlas.
• Experimental validation of findings in Drosophila models.

Main Results:

• Drosophila organs scale via distinct strategies (cell size, cell number, or both) in an allometric, not uniform, manner.
• Female flight muscles increase cell number (myoblasts), while female hearts maintain cardiomyocyte number despite larger size.
• Female fat body cells are larger with increased ribosomal protein expression, whereas males have a greater number of fat body cells.

Conclusions:

• Sex-specific allometry in cell size and nuclear number provides the cellular basis for sexual dimorphism in Drosophila.
• This study offers a framework for understanding sex differences in organ size across species and biological systems.