Genotype-phenotype correlation in satellited 1p chromosome: Importance of fluorescence in situ hybridization (FISH) applications

Fluorescence in situ hybridization (FISH) was used to delineate the structural rearrangement of two satellited 1p chromosomes identified in a prenatal and in a postnatal case. Prenatal case: chromosome analysis of amniotic cells on a 37-year-old G2, PO, SAb1 woman, referred for advanced maternal age, revealed a 46,XX,1ps karyotype. Parental chromosome analyses showed that the satellited chromosome was paternal in origin. The satellited 1p did not stain with NOR and DA-DAPI. FISH using a probe specific for the rDNA, 18S and 28S genes also showed no hybridization to the satellited 1p. Using two different probes specific for 1p36.3 showed hybridization to both chromosomes 1p. This indicated that the terminal band was most likely present in the fetus and chromosomally balanced like the father. The pregnancy was continued and a phenotypically normal female was born. Postnatal case: Chromosome analysis of peripheral lymphocytes was performed on a 3 1/2-year old female with multiple congenital anomalies including growth retardation, developmental delay, upslanted palpebral fissures, thick eyebrows, esotropia, seizures, and mental retardation. She was born to a 14-year old, G1, PO mother, after a full-term pregnancy, by cesarian-section due to breech presentation. Her one-year-old brother is reportedly in good health. Chromosome analysis revealed amore » de novo 46,XX,lps. NOR and DA-DAPI stains were positive indicating the satellites are most likely chromosome 15 in origin. FISH using the rDNA probes also showed a hybridization to the 1ps. The two 1p36.3 probes showed only one signal to the normal chromosome 1, indicating a deletion which resulted in monosomy of 1p36.3. The clinical features of the child correlates with published cases of the terminal deletions of 1p.« less