A rare chromosome 5 heterochromatic variant derived from insertion of 9qh satellite 3 sequences

A new multicolor fluorescence in situ hybridization probe set directed against human heterochromatin: HCM-FISH

A new multicolor fluorescence in situ hybridization (mFISH) probe set is presented, and its possible applications are highlighted in 25 clinical cases. The so-called heterochromatin-M-FISH (HCM-FISH) probe set enables a one-step characterization of the large heterochromatic regions within the human genome. HCM-FISH closes a gap in the now available mFISH probe sets, as those do not normally cover the acrocentric short arms; the large pericentric regions of chromosomes 1, 9, and 16; as well as the band Yq12. Still, these regions can be involved in different kinds of chromosomal rearrangements such as translocations, insertions, inversions, amplifications, and marker chromosome formations. Here, examples are given for all these kinds of chromosomal aberrations, detected as constitutional rearrangements in clinical cases. Application perspectives of the probe set in tumors as well as in evolutionary cytogenetic studies are given.

Prenatal diagnosis of a rare inherited heterochromatic variant chromosome 4

Heterochromatic chromosome polymorphisms have been extensively reported. Most are associated with C-band positive regions located on chromosomes 1, 9, 16, and Y. We report a prenatal case of a rare heterochromatic variant on chromosome 4. Amniocentesis was performed on a 35-year-old white female for AMA. The karyotype was 46,XY,add(4)(q35)?. One chromosome 4 homolog had an additional dark band at the terminus of the long arm. Parental chromosome analyses revealed that the chromosome 4 was maternally inherited. The mother and fetus were both Q and C-band positive and NOR and DAPI Distamycin staining negative. FISH using Y, 4, and 9 whole chromosome paint (WCP), centromere probes for all chromosomes (Cytocell, Chromoprobe Multiprobe-I System, Rainbow Scientific, Inc., Windsor, CT), alpha-satellite probes for 13/21, 14/22 (D13Z1/D21Z1; D14Z1/D22Z1, Oncor, Gaithersburg, MD), and the 15 PWS/Angelman probe (LSI SNRPN, D15Z1, PML, Vysis, Inc., Downers Grove, IL) were negative. The TelVysion 4q telomere probe (D4S2930, Vysis, Inc.) was positive. A phenotypically normal male was born at 37 weeks. Follow up studies on placenta, cord, cord blood, and foreskin confirmed the prenatal results. Based on these findings, it appears that this chromosome 4 was a rare heterochromatic variant. Heterochromatic variants have been demonstrated to have no phenotypic effect on carriers. This case illustrates the importance of reporting unusual variant chromosomes for genetic counseling purposes. To the best of our knowledge, this is the first report of a heterochromatic variant involving part of the long arm of chromosome 4 in a phenotypically normal mother and child.

A review of fluorescence in situ hybridization (FISH): current status and future prospects

Fluorescence in situ hybridization (FISH) is a powerful technique for detecting DNA or RNA sequences in cells, tissues and tumors. This molecular cytogenetic technique enables the localization of specific DNA sequences within interphase chromatin and metaphase chromosomes and the identification of both structural and numerical chromosome changes. FISH is quickly becoming one of the most extensively used cytochemical staining techniques owing to its sensitivity and versatility, and with the improvement of current technology and cost effectiveness, its use will surely continue to expand. Here we review the wide variety of current applications and future prospects of FISH technology.