# SIX3 as a Regulator of Development and Disease

## TL;DR

This review explores the SIX3 and SIX6 subfamily of transcription factors, their roles in development, and their links to diseases like cancer and diabetes.

## Contribution

The paper provides a comprehensive overview of the SIX3–SIX6 subfamily's regulatory roles and their implications in disease mechanisms.

## Key findings

- SIX3 can act as a tumor suppressor or a marker of poor prognosis in various cancers.
- SIX3 and SIX2 are involved in pancreatic β-cell identity and stability.
- Downregulation of SIX2 and SIX3 disrupts β-cell homeostasis and contributes to type 2 diabetes.

## Abstract

Transcriptional regulation is pivotal for developmental processes and cell fate specification in homeostasis. One particularly relevant group of transcription factors is the sine oculis homeobox (SIX) family, which is involved in a wide range of molecular processes from development to tissue maintenance. Within this family, distinct subfamilies exhibit specific DNA-binding preferences and can function as transcriptional activators or repressors. In this review, we focus on the Optix/SIX3–SIX6 subfamily and discuss their roles as transcriptional regulators, as well as the consequences of their deregulation for neuronal and ocular development and for the maintenance of tissue homeostasis. We further examine how SIX3 can act either as a tumour suppressor or as a marker of poor prognosis in different cancer types. Moreover, we summarize recent findings on the role of SIX3 in pancreatic β cells and highlight emerging evidence that SIX2 also contributes to β-cell identity and regulatory stability. Downregulation of SIX2 and SIX3 alters gene regulatory programs associated with β-cell homeostasis and contributes to type 2 diabetes. As accumulating evidence links members of the SIX family to cancer and metabolic disease, it is crucial to characterize how these transcription factors regulate cell identity, with important implications for disease mechanisms and therapeutic strategies.