Abstract
We have further characterized an unusual 22p + marker chromosome with a double nucleolus organizer region (dNOR) previously identified in a family with late-onset dementia of the Alzheimer type. G-banding and morphology of the marker's q arm were typically normal. However, the p + arm had a terminal cytological satellite and a GT-positive region at the midpoint. Standard C- banding documented 2 C-positive regions: one was associated with the primary centromere; the other, which was at the midpoint of the p arm, was not associated with a constriction. With replication-banding, there was a darkly staining region in the middle of the p + arm that resembled the pericentromeric region of a chromosome 21 or 22. Fluorescence in situ hybridization with pXlr 101, a probe recognizing the full repeating unit of rDNA, indicated that the marker had an unusually large rDNA region; with pU 1.2, a probe recognizing the human rDNA promoter, the signal was a doublet. The marker had 2 signals with a β-satellite probe, and a second signal in addition to that present at the primary centromere under low stringency with α-satellite probes and a classic satellite probe. Immunostaining of chromosome spreads after R-banding and ultraviolet (UV) denaturation showed that the major portion of the marker's p arm was highly methylated.
Original language | English (US) |
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Pages (from-to) | 14-19 |
Number of pages | 6 |
Journal | American Journal of Medical Genetics |
Volume | 47 |
Issue number | 1 |
State | Published - 1993 |
Externally published | Yes |
Keywords
- Alzheimer disease
- chromosome 22
- double nucleolus organizer region
ASJC Scopus subject areas
- Genetics(clinical)