Alternative splicing and start sites: Lessons from the Grainyhead-like family

- Highlight potential for differential transcriptional modulation of downstream targets by TFs with alternate gene products.
- Provide insights into the practical/experimental consequences that existence of alternative gene products has on development.
- Provide an overview of the Grainyhead-like gene family and their roles during development and genetic disease.
- Grhl genes as a case study to illustrate importance of splicing and protein isoform function during development and disease.

The two main mechanisms that expand the proteomic output of eukaryotic genes are alternative splicing and alternative translation initiation signals. Despite being essential to generate isoforms of gene products that create functional diversity during development, the impact of these mechanisms on fine-tuning regulatory gene networks is still underappreciated. In this review, we use the Grainyhead-like (Grhl) family as a case study to illustrate the importance of isoforms when investigating transcription factor family function during development and disease, and highlight the potential for differential modulation of downstream target genes. We provide insights into the importance of considering alternative gene products when designing, undertaking, and analysing primary research, and the effect that isoforms may have on development. This review also covers known mutations in Grhl family members, and postulates how genetic changes may dictate transcriptional specificity between the Grhl family members. It also contrasts and compares the available literature on the function and importance of the Grhl isoforms, and highlights current gaps in our understanding of their regulatory gene networks in development and disease.