Somatic pairing between subtelomeric chromosome regions: implications for human genetic disease?

Fluorescence in-situ hybridization (FISH) has been used to study the spatia l orientation of subtelomeric chromosome regions in the interphase nucleus. Compared to interstitial chromosomal sites, subtelomeres showed an increas ed number of somatic pairings. However, pairing frequency also depended on the specific regions involved and varied both between different subtelomere s and between different interstitial regions. An increased incidence of som atic pairing may play at least some role in the frequent involvement of the subtelomeres in cytogenetically cryptic chromosome rearrangements. In pati ents suffering from facioscapulohumeral muscular dystrophy (FSHD), which is associated with a deletion of subtelomeric repeats, the FSHD region on 4qt er showed a changed pairing behavior, which could be indicative of a positi on effect and/or trans-sensing effect as a cause for disease.