Expressed in the adrenal gland. TNX genes are located in the class III HLA region within a complex locus, named RCCX module, containing genes for RP1/STK19, C4B, CYP21B/CYP21A2 and TNXB. Most chromosomes bear 2 modules, but monomodular and trimodular haplotypes are common in most populations. The bimodular haplotype results from the duplication of the RCCX module, leading to a duplicate containing RP2/RP1 pseudogene, C4A, CYP21A/CYP21A1P and TNXA. TNXA is a duplicated section of TNXB and probably consists in a truncated pseudogene: it contains a 120 bp deletion causing a frameshift and a premature stop codon that probably render the gene non-functional. In some pathologies, an unequal crossover between monomodular and bimodular RCCX results in a chromosome with a TNXB-TNXA hybrid gene, arising from a fusion between the TNXB gene of a monomodular RCCX and the TNXA gene of a bimodular RCCX. The TNXB-TNXA hybrid may correspond to TNXB-Short gene and may produce a functional protein. Could be the product of a pseudogene. TNXA is transcriptionally active in adrenal cortex but no protein product has been observed.