LIUBICICH, Danielle M.*; SERANO, Julia M.; PATEL, Nipam H.; University of California, Berkeley/HHMI; University of California, Berkeley/HHMI; University of California, Berkeley/HHMI: Functional approaches to understanding the role of hox genes in specifying crustacean appendage identity

Specialization of crustacean trunk appendages may require the presence and absence of certain hox genes. Hox genes are highly conserved transcription factors that play a role in regionalization of animal body plans. Previous comparative analysis of one hox gene, Ultrabithorax (Ubx), in a variety of crustaceans illustrated a correlation between boundaries of gene expression and limb specialization in the crustacean trunk. While most trunk segments express Ubx and develop walking legs, trunk segments lacking Ubx expression develop as feeding appendages called maxillipeds. We have analyzed the expression patterns of all hox genes present in the amphipod crustacean Parhyale hawaiensis. From this analysis, we propose that it is the combination of Sex combs reduced (Scr) and Antennapedia (Antp) expression, in the absence of Ubx expression, in trunk segments that controls maxilliped specification in Parhyale. We are testing this hypothesis using gene knockdown techniques to further understand the function of each gene during Parhyale development. Traditional RNAi methods of injecting double-stranded RNA into embryos does not produce a permanent reduction in gene expression nor phenotype for individual hox genes. We are we are currently designing an alternative method to continuously express inverted repeat transcripts throughout development to knockdown gene expression. These experiments may potentially highlight mechanisms by which changes in gene expression can influence the evolution and development of morphological diversity in crustacean appendages.