Thymosin-β4 is expressed in the developing human heart.

A) Detection of TMSB4X cDNA (278 bp) by PCR in human fetal atria and ventricle samples. Alongside each cDNA sample a corresponding 'no reverse transcriptase' negative control sample (-ve control) was run. Representative of three individual hearts (7–8 pcw). B-G) Fluorescent immunostaining for Tβ4 protein indicates localisation to specific cells in both the ventricle (B, C, D, E) and atria (F & G), as well as to the epicardium (open arrows) and endocardium (closed arrows). DAPI nuclear staining is also shown (D & G). Within the ventricle walls, staining was more intense in the interventricular septum (IVS) and compact layer (C), compared to the trabecular layer (T). Representative of six individual hearts (7–12 pcw). Scale bars = 200 μm (B), 150 μm (C, D, F, G), 100 μm (E).