# Epigenetic, Genetic, and Functional Germline Alterations of PAX Genes in Human Pathology: A Comprehensive Update

## TL;DR

This paper reviews how mutations in PAX genes lead to various human diseases, emphasizing their role in development and disease mechanisms.

## Contribution

The paper offers a comprehensive overview of germline PAX gene mutations and their clinical implications across multiple organ systems.

## Key findings

- Germline mutations in PAX genes are linked to a range of congenital disorders with variable expressivity and overlapping symptoms.
- PAX proteins play roles in postnatal tissue maintenance and immune function, expanding their clinical relevance beyond embryonic development.
- The paper integrates molecular genetics with human pathology to clarify genotype–phenotype correlations and disease classification.

## Abstract

Paired box (PAX) genes encode a family of nine transcription factors that function as master regulators of embryogenesis, organogenesis, and lineage specification. Their tightly regulated spatial and temporal expression is essential for the development of multiple organ systems, including the central nervous system, eyes, kidneys, immune system, musculoskeletal system, and endocrine organs. Germline mutations of PAX genes result in a broad and often pleiotropic spectrum of human disease, reflecting the developmental programs governed by each family member. Pathogenic variants in PAX genes underlie diverse congenital disorders such as aniridia (PAX6), renal coloboma syndrome (PAX2), otofaciocervical syndrome with immunodeficiency (PAX1), Waardenburg syndrome (PAX3), maturity-onset diabetes of the young (PAX4), and tooth agenesis (PAX9). These conditions frequently demonstrate variable expressivity, incomplete penetrance, and overlapping phenotypes, which make it challenging to be clinically recognized. Beyond embryogenesis and embryologic development, emerging evidence indicates that several PAX proteins remain active in postnatal tissue maintenance, adult stem cell regulation, immune function, and regenerative responses (particularly PAX7 in skeletal muscle satellite cells and PAX5 in B-cell homeostasis), further expanding their clinical relevance. This review provides a synopsis of the major, clinically relevant, germline PAX gene mutations, emphasizing genotype–phenotype correlations, developmental mechanisms, and disease classification across the organ systems. By integrating molecular genetics with human pathology, we highlight the diagnostic implications of PAX genes as central determinants of congenital disease and provide a framework for understanding how alterations in the developmental transcriptional networks translate into human pathology.