CF2 represses Actin 88F gene expression and maintains filament balance during indirect flight muscle development in Drosophila.

Kathleen M Gajewski,Robert A Schulz,Alexander Idnurm

doi:10.1371/journal.pone.0010713

Kathleen M Gajewski, Robert A Schulz + Show 1 more

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https://doi.org/10.1371/journal.pone.0010713

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Abstract

The zinc finger protein CF2 is a characterized activator of muscle structural genes in the body wall muscles of the Drosophila larva. To investigate the function of CF2 in the indirect flight muscle (IFM), we examined the phenotypes of flies bearing five homozygous viable mutations. The gross structure of the IFM was not affected, but the stronger hypomorphic alleles caused an increase of up to 1.5X in the diameter of the myofibrils. This size increase did not cause any disruption of the hexameric arrangement of thick and thin filaments. RT-PCR analysis revealed an increase in the transcription of several structural genes. Ectopic overexpression of CF2 in the developing IFM disrupts muscle formation. While our results indicate a role for CF2 as a direct negative regulator of the thin filament protein gene Actin 88F (Act88F), effects on levels of transcripts of myosin heavy chain (mhc) appear to be indirect. This role is in direct contrast to that described in the larval muscles, where CF2 activates structural gene expression. The variation in myofibril phenotypes of CF2 mutants suggest the CF2 may have separate functions in fine-tuning expression of structural genes to insure proper filament stoichiometry, and monitoring and/or controlling the final myofibril size.

Highlights

The indirect flight muscles (IFM) of Drosophila are exquisitely adapted to provide the maximum power to the wings
To examine the expression of Chorion factor 2 (CF2) transcript during development of the flight muscles, we used RT-PCR on cDNA from the dissected IFM of adults, 40 hr after pupa formation (APF) pupae, and 60 hr APF pupae
In this paper we investigate the expression pattern and function of the Zn finger transcription factor CF2 in adult flight muscle development

Summary

Introduction

The indirect flight muscles (IFM) of Drosophila are exquisitely adapted to provide the maximum power to the wings They contain unique isoforms of structural proteins such as actin, the troponins, and myosin heavy chain (mhc). Flies that are doubly heterozygous for null mutations in mhc and Act 88F ( having a 1:1 mhc: actin ratio) can fly, not as well as wild type (with a 2:2 ratio) [3] It is not just the amounts of these proteins, and their stoichiometry, that influences flight muscle structure and function

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