| Group Xeroderma pigmentosum | Human Chromosome Location | Central Nervous System Disorders | Relative Repair (%) |
|---|---|---|---|
| A | 9q34.1 | Yes | 2-5 |
| B (Cockayne and ERCC3)* | 2q21 | Yes | 3-7 |
| C | 3q25 | No | 5-20 |
| D (Cockayne)*,† | 19q13.2 | Yes | 25-50 |
| E | –– | No | 50 |
| F | 16q13.1 | No | 18 |
| G | 13q32.3 | Yes | < 2 |
| Variant | –– | No | 100 |
| CHO (ERCC)‡ | |||
| 1 | 19q13.2 | –– | Low |
| 2 (XPD) | 19q13.2 | –– | Intermediate |
| 3 (XPB) | 2q21 | –– | Intermediate |
| 4 (XPF) | 16q13.1 | –– | Low |
| 5 (XPG) | 13q 32.3 | –– | Intermediate |
Patients also exhibit symptoms commonly associated with Cockayne syndrome: dwarfism, cutaneous features, and mental retardation. Group B and ERCC3 represent the same complementation group as do Group D and ERCC2, F and ERCC4, G and ERCC5.
Some patients also have symptoms of trichothiodystrophy.
Genes in the ERCC series are found in human and rodent cells, and were first identified through selection of UV-sensitive hamster cells. ERCC1 does not correspond to any XP group, but ERCC3 and XP group B are identical. There are 8 or more CHO complementation groups, but the higher numbered groups are rare and still being characterized. Relative repair in the ERCC series is classified approximately on the basis of relative sensitivity to DNA damage. [The author is grateful to L.H. Thompson for providing this summary of gene locations and group assignments.]
From: Chapter 15, Ultraviolet Radiation Carcinogenesis
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