Mosaic loss of 15q11q13 in a patient with hypomelanosis of Ito: Is there a role for the P gene?
- Children`s Hospital of Philadelphia, PA (United States); and others
Hypomelanosis of Ito (HMI) is a heterogeneous and clinically variable disorder characterized by specific patterns of hypopigmentation on the limbs and trunk. Many different mosaic chromosomal abnormalities have been reported with this condition leading to the hypothesis that HMI may be a non-specific marker of chromosome mosaicism. We studied a patient with dysmorphia, mental retardation, behavioral disturbances and HMI. Cytogenetic analysis demonstrated that he was mosaic for an unbalanced translocation, 45,XY,-7,-15,+der(7)t(7;15)(q34;q13)/46,XY in both blood and skin rendering him monosomic for 7q34 to qter and 15pter to q13 in the cells containing the translocation. The human homologue (P) of the p gene, the product of the mouse pink-eyed dilution locus, maps to 15q11q13. Loss of this locus is believed to be the cause of the hypopigmentation seen in patients with deletions of 15q11q13 and the Prader-Willi and Angelman syndromes. Mutations within the P gene have also been associated with tyrosinase positive (type II) oculocutaneous albinism. By fluorescence in situ hybridization we demonstrated that our patient is deleted for one copy of the P gene in the cells with the unbalanced translocation as well as for two probes from the Prader-Willi/Angelman critical region. The myl gene, which maps to 15q22, was present on the translocated chromosome as expected. There is a previous report in the literature of an HMI patient who was mosaic for del(15)(q11), although the copy number of the P gene was not specifically determined. Although hypomelanosis of Ito is a heterogeneous disorder, we postulate that in our case, and potentially in others, this phenotype may result from loss of a specific pigmentation gene.
- OSTI ID:
- 133738
- Report Number(s):
- CONF-941009-; ISSN 0002-9297; TRN: 95:005313-0469
- Journal Information:
- American Journal of Human Genetics, Vol. 55, Issue Suppl.3; Conference: 44. annual meeting of the American Society of Human Genetics, Montreal (Canada), 18-22 Oct 1994; Other Information: PBD: Sep 1994
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BASIC STUDIES
HUMAN CHROMOSOME 15
CHROMOSOMAL ABERRATIONS
MOSAICISM
GENETIC MAPPING
PATIENTS
CONGENITAL MALFORMATIONS
MENTAL DISORDERS
KARYOTYPE
BEHAVIOR
PHENOTYPE
GENES
STRUCTURE-ACTIVITY RELATIONSHIPS
GENE MUTATIONS
HUMAN CHROMOSOME 7
PIGMENTS
DNA HYBRIDIZATION
FLUORESCENCE
PROBES