Expression of exon-8-skipped kindlin-1 does not compensate for defects of Kindler syndrome.

BACKGROUND

Kindler syndrome (KS) is a rare, inherited skin disease characterized by blister formation and generalized poikiloderma. Mutations in KIND1, which encodes kindlin-1, are responsible for KS. c.1089del/1089+1del is a recurrent splice-site deletion mutation in KS patients.

OBJECTIVE

To elucidate the effects of c.1089del/1089+1del at the mRNA and protein level.

METHODS

Two KS patients with c.1089del/1089+1del were included in this study. Immunofluorescence analysis of KS skin samples using antibodies against the dermo-epidermal junction proteins was performed. Exon-trapping experiments were performed to isolate the mRNA sequences transcribed from genomic DNA harbouring c.1089del/1089+1del. β1 integrin activation in HeLa cells transfected with truncated KIND1 cDNA was analyzed.

RESULTS

Immunofluorescence study showed positive expression of kindlin-1 in KS skin with c.1089del/1089+1del mutation. We identified the exon-8-skipped in-frame transcript as the main product among multiple splicing variants derived from that mutation. HeLa cells transfected with KIND1 cDNA without exon 8 showed impaired β1 integrin activation. Exon-8-coding amino acids are located in the FERM F2 domain, which is conserved among species, and the unstructured region between F2 and the pleckstrin homology domain.

CONCLUSION

This study suggests that exon-8-skipped truncated kindlin-1 is functionally defective and does not compensate for the defects of KS, even though kindlin-1 expression in skin is positive.