Fig. 7: CD44 is a direct target of CELF6, and LINC01594 regulates CD44 V4–V7 exon skipping by modulating CELF6.

A The CD44 protein is composed of an extracellular link domain, a stalk-like region in the extracellular domain close to the transmembrane region, where the variant exon products (red) are inserted, the transmembrane region (TM) and the cytoplasmic tail (CP). CD44v contains one or several variant regions (consisting of V1, V2, V3, V4, …V10), and various exons may constitute different CD44 variant isoforms via alternative splicing. B Representative images of semiquantitative PCR from HCT116 and LoVo cells following LINC01594 knockdown. The forward primer was designed on exon 2, and the reverse primers were designed on exon 15 and exon 16 of CD44 mRNA. The production of CD44s was 690 bp, and CD44v > 690 bp. C qRT‒PCR revealed that LINC01594-mediated CELF6 expression was reversed by CELF6 knockdown. (n = 3). *p < 0.05, **p < 0.01. D Rescue tests showed that knockdown of LINC01594 and CELF6 reversed the loss in CD44v expression induced by LINC01594 knockdown alone. E Semiquantitative PCR tested the expression level of CD44v isoforms in SW480 and LoVo cells with CELF6 overexpression. F Primers were designed to detect CD44 v4–v7 expression in CELF6-overexpressing and CELF6-silenced SW480 and LoVo cells. The forward primer was designed on variant exon 4 (v4), and the reverse primer was designed on variant exon 7 (v7). The production length was 429 bp. G The CD44 forward primer was designed on exon 15 and exon 16, and the reverse primer was designed on exon 18 to determine the expression of the CD44 standard isoform. H Transwell assays were conducted to examine the effect of CD44 v4–v7 isoform overexpression and knockdown on SW480 and LoVo cells. (n = 3). ***p < 0.001.