Interphase FISH analysis of the PLP gene in Pelizaeus-Merzbacher disease. G.H. Vance1, O. Henegariu2, V.C. Thurston1, L. Sendi1, S. Dlouhy1, J.A. Trofatter3, M.E. Hodes1. 1) Dept Med & Molec Genetics, Indiana Univ, Indianapolis, IN; 2) Dept of Genetics, Yale University, New Haven, CT; 3) Dept Psychiatry, Indiana Univ, Indianapolis, IN.
The proteolipid protein gene, PLP, encodes the major protein of myelin of the central nervous system. Duplications of the PLP gene have been observed in patients with Pelizaeus-Merzbacher disease (PMD), an X-linked neurodegenerative disease. Duplication analysis of five affected males and their carrier mothers has been reported using dual-color probes of both the PLP gene and alpha satellite region of the X chromosome[1]. In contrast to this published report, we have established two-color interphase FISH analysis for the PLP gene duplication in our cytogenetic laboratory with a cosmid for Xq rather than an X alpha satellite probe. The PLP probe, cosmid 350.1 was labeled with digoxigenin and a 40 kb cosmid, cos 9, was labeled with biotin. Both probes were hybridized to slides with fixed cells of established lymphoblastoid cell lines from 32 PMD family members (7 females and 25 males). One hundred nuclei for each sample were scored on a grid comparing the number of green (1-2) with the number of red (1-4) signals. Duplication mutations were detected in 44% of these individuals. Four females were duplication carriers and 10 affected males were carriers. It is now clear that PLP gene duplication is a significant mutation in the etiology of Pelizaeus-Merzbacher disease.
[1] Woodward K, Kendall E, Vetrie D, Malcolm S. Pelizaeus-Merzbacher Disease: Identification of Xq22 Proteolipid-Protein Duplications and Characterization of Breakpoints by Interphase FISH. Am J Hum Genet 63:207-217, l998.