RBM10 in complete hydatidiform mole: cytoplasmic occurrence of its 50 kDa polypeptide

Abstract

Background: RNA-binding motif protein 10 (RBM10), originally identified as S1-1 protein, is a nuclear protein with likely functions in transcription and RNA splicing. The RBM10 gene maps to the X chromosome and, in female cells, is inactivated in one of the two X chromosomes near the boundary with genes escaping inactivation. This study investigated the occurrence of the RBM10 gene product in complete hydatidiform mole, which is composed of cells with paternal diploid chromosomes (46, XX).

Methods: Deparaffinized normal chorion or complete hydatidiform mole tissues were hybridized with a fluorescein-conjugated RBM10 gene probe in fluorescent in situ hybridization (FISH) analysis. Immunohistochemistry and immunoelectron microscopy of the tissues were performed using an anti-RBM10 antiserum. Proteins from complete hydatidiform mole tissues and those separated by anti-RBM10-linked affinity chromatography were also examined by western blotting.

Results: As expected, the RBM10 gene was detected by FISH as double spots in the nuclei of complete hydatidiform mole cells. Immunohistochemistry revealed a nuclear presence of RBM10 in normal chorion and complete hydatidiform moles, and a notable cytoplasmic presence in complete hydatidiform moles. Western blotting and immunoaffinity chromatography revealed that a 50 kDa protein was predominantly found in the cytosolic fraction of complete hydatidiform moles.

Conclusions: A 50 kDa protein with common antigenicity to RBM10 was found in the cytoplasm of complete hydatidiform mole cells, and could represent one of the characteristics of the disease.