HoxA

HOXA refers to the HOXA gene cluster, one of the four HOX gene clusters in vertebrates, which encodes transcription factors that regulate embryonic development along the body's anterior-posterior axis. In humans, the HOXA cluster contains HOXA1 through HOXA13, located on chromosome 7. Each HOXA gene encodes a protein with a conserved homeodomain that binds DNA to control transcription of downstream targets.

The HOXA cluster shows spatial and temporal colinearity: the genes at the 3' end are typically expressed earlier and in more anterior structures, while the 5' genes are expressed later and in posterior regions. Regulation is complex and involves distant enhancers, epigenetic controls, and noncoding RNAs that coordinate expression during development.

HOXA genes contribute to hindbrain segmentation, pharyngeal arch patterning, limb development, and axial skeleton formation. HOXA13, in particular, is important for limb and genitourinary tract development, with mutations causing limb and digit defects such as hand-foot-genital syndrome. The specific roles of individual HOXA genes depend on tissue context and interactions with other HOX proteins and cofactors.

Clinical relevance includes congenital anomalies arising from HOXA misregulation and altered expression patterns in cancer. Demethylation or rearrangements leading to HOXA overexpression, notably HOXA9 and related paralogs, are associated with hematologic malignancies such as acute myeloid leukemia, particularly in cases with MLL gene rearrangements. Aberrant HOXA activity may also appear in some solid tumors.

HOXA remains a focus of developmental biology and cancer research due to its conserved role in pattern formation and lineage specification.