tenascin-XA; TN-XA (TNXA XA)

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Structure

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 & TNXB
most chromosomes bear 2 modules, but monomodular & 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 & TNXA
TNXA is a duplicated section of TNXB & probably consists in a truncated pseudogene: it contains a 120 bp deletion causing a frameshift & a premature stop codon that probably render the gene non-functional
in some pathologies, an unequal crossover between monomodular & bimodular RCCX results in a chromosome with a TNXB-TNXA hybrid gene, arising from a fusion between the TNXB gene of a monomodular RCCX & the TNXA gene of a bimodular RCCX
the TNXB-TNXA hybrid may corresponds to TNXB-short gene & 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