XHAPLN3 plays a key role in cardiogenesis by maintaining the hyaluronan matrix around heart anlage

Hyaluronan matrix plays an important role during vertebrate cardiogenesis. Transcripts for the hyaluronan synthase Has2 gene are expressed in heart anlage, and disruption of either Has2 or versican, a hyaluronan matrix component, abrogates normal cardiac morphogenesis. However, the mechanisms by which hyaluronan matrix contributes to early heart development are largely unknown. Here we show that Xenopus hyaluronan and proteoglycan-binding link protein 3 (XHAPLN3) helps to maintain hyaluronan matrix around the cardiac anlage, and thereby contribute to cardiogenesis. XHAPLN3 mRNA transcript localization overlapped with the mRNA expression of both Xhas2 and Xversican at the heart anlage of early tailbud (stage 23) embryos. Furthermore, knockdown of XHAPLN3 or Xhas2 with morpholino antisense oligos caused a heart deficiency in developing tadpoles. Our results show when and how components of the hyaluronan matrix function in cardiogenesis, improving our understanding of how extracellular matrix participates in embryogenesis.