Moreover, the following genes were up-regulated: LRRC15 (leucine-rich repeat-containing protein 15), which may function in cell communication; LHX2 (LIM homeobox 2), which maintains stem cell characteristics in HF; VSIG8 (V-set and immunoglobulin domain-containing protein 8), which is enriched in the cuticle; and PRR9 (proline-rich protein 9), which serves as substrates for transglutaminases that are responsible for cross-linking (S3 Table) [31, 32]. This evidence concerns the gene PRR9 and hydrops fetalis.