Subterranean Fishes of the World

4305

2019

AIM 2019

57

The role of maternal effects is poorly understood but likely to be critical for a complete understanding of Astyanax mexicanus cavefish (CF) development and evolution. Reciprocal hybridization studies revealed that the degenerative CF optic phenotype, including modified optic polarity, lens survival, and sclera morphology, is influenced by maternal genetic effects. Additional studies suggested that maternal factors may be involved in modifying CF dorsoventral patterning through effects on the Wnt/ß-catenin signaling cascade. To obtain more comprehensive information about the diversity and nature of maternal transcripts, we compared the unfertilized egg transcriptomes of A. mexicanus surface fish (SF), Pachon CF (PA-CF), and Tinaja CF (TI-CF) by RNAseq using the BGISEQ-500 platform. Of a total of 24,776 maternal transcripts, we identified 1649 (6.7%) upregulated transcripts and 1471 (5.9%) downregulated transcripts in PA-CF eggs relative to SF eggs, and 1138 (4.6%) upregulated transcripts and 1162 (4.7 %) downregulated transcripts in TI-CF eggs relative to SF eggs. Of the top 100 differentially expressed CF transcripts, 30 upregulated transcripts and 44 downregulated transcripts are represented in both the PA-CF and TI-CF egg transcriptomes, suggesting that they may be important for the execution of CF maternal effects. The CF up/down regulated transcripts function in pathways mainly related to lipid and carbohydrate metabolism, environmental adaptation, protein processing, and transcriptional regulation. The transcriptome analysis also revealed significant upregulation of axin1 transcripts in TI-CF eggs relative to SF eggs, as previously found in PA-CF eggs. Thus, Axin1, which modulates dorsal embryonic fates by mediating ß-catenin degradation, is an excellent candidate for a maternal determinant controlling the change in dorsoventral polarity of CF embryos. This study expands our knowledge of maternal transcripts in A. mexicanus and provides a foundation for future molecular analysis of maternal genetic effects in CF development and evolution.

1

Astyanax Interrnational Meeting