Long-range mapping of the 11q23 region involved in chromosome aberrations in human tumors by pulsed-field gel electrophoresis with a yeast artificial chromosome

From 1957 to Nowadays: A Brief History of Epigenetics

Due to the spectacular number of studies focusing on epigenetics in the last few decades, and particularly for the last few years, the availability of a chronology of epigenetics appears essential. Indeed, our review places epigenetic events and the identification of the main epigenetic writers, readers and erasers on a historic scale. This review helps to understand the increasing knowledge in molecular and cellular biology, the development of new biochemical techniques and advances in epigenetics and, more importantly, the roles played by epigenetics in many physiological and pathological situations.

Molecular analysis of an unstable genomic region at chromosome band 11q23 reveals a disruption of the gene encoding the alpha2 subunit of platelet-activating factor acetylhydrolase (Pafah1a2) in human lymphoma

A region of 150 kb has been analysed around a previously isolated, lymphoma associated, translocation breakpoint located at chromosome band 11q23. This balanced and reciprocal translocation, t(11;14)(q32;q23), has been shown to result in the fusion between chromosome 11 specific sequence and the switch gamma4 region of the IGH locus. The LPC gene, encoding a novel proprotein convertase belonging to the furin family, has been identified in this region. In order to characterize further the region surrounding the translocation, we have determined the detailed structure of LPC. Here we show that LPC consists of at least 16 exons covering 25 kb, and that there is a partial duplication, involving mobile genetic elements and containing LPC exons 13-17 in a tail-tail configuration at 65 kb downstream. Since the chromosomal breakpoint lay between these two structures, the intervening region was further analysed and shown to contain at least two unrelated genes. The previously known SM22 gene was localized close to the 3' tail of LPC. Furthermore, we identified the gene encoding the alpha2 subunit of platelet-activating factor acetylhydrolase (Pafah1a2) at the chromosomal breakpoint. The position of another previously identified breakpoint was also located to within the first intron of this gene. Altogether, our results give evidence of a genomic instability of this area of 11q23 and show that Pafah1a2 and not LPC is the gene disrupted by the translocation, suggesting that deregulated Pafah1a2 may have a role in lymphomagenesis.

Molecular cytogenetics localizes two new breakpoints on 11q23.3 and 21q11.2 in myelodysplastic syndrome with t(11;21) translocation

Translocation t(11;21)(q24;q11.2) is a rare but recurrent chromosomal abnormality associated with myelodysplastic syndrome (MDS) that until now has not been characterized at the molecular level. We report here results of a molecular cytogenetic analysis of this translocation in a patient with refractory anemia. Using FISH with a panel of 11q and 21q cosmid/YAC probes, we localized the chromosome 11 breakpoint at q23.3 in a region flanked by CP-921G9 and CP-939H3 YACs, distal to the HRX/MLL locus frequently involved in acute leukemias. The chromosome 21 breakpoint was mapped in a 800-kb fragment inserted into the CP-145E3 YAC at 21q11.2, proximal to the AML1 gene. It is noteworthy that in all four cases with a t(11;21) reported until now, a second der(11)t(11;21) and loss of normal chromosome 11 could be observed either at diagnosis or during the course of the disease. Since in our case heteromorphism was detected by FISH on the centromeric region of the two der(11), the second der(11) chromosome could be the result of a mitotic recombination that had occurred on the long arm of chromosome 11, rather than of duplication of the original der(11). Constancy of secondary karyotypic changes resulting in an extra copy of the putative chimeric gene at der(11), loss of 11 qter sequences, and partial trisomy 21 suggest that neoplastic progression of MDS cases with a t(11;21) may be driven by the same mechanism(s).

Chromosomal changes observed in immortalized human keratinocytes transformed by ionizing radiation

Human epithelial cancer cells were induced by concerted action of DNA tumor virus and X-ray radiation. Treatment of nontumorigenic early passage AD12-SV40 immortalized epithelial cells (RHEK-1) at passage 23 with radiation, resulted in further changes in their growth properties. One day old cultures of these RHEK-1 cells were irradiated with graded doses of X-rays (0, 2, 4, 6, and 8 Gy i.e. RHEK-1, RHEK-1/200R, RHEK-1/400R, RHEK-1/600R, and RHEK-1/800R). Morphologic alterations, the ability to grow in soft agar, and to form rapidly-growing squamous cell carcinomas in nude mice were concomitantly acquired properties of the radiation transformed cell lines RHEK-1/200R and RHEK-1/ 400R. On the basis of commonality in having addition of some extra material in chromosome 11 in the region between q14/q22 in all tumorigenic cell lines RHEK-1/200R and RHEK-1/400R, and deletion of the same region in nontumorigenic irradiated cell lines-RHEK-1/600R and RHEK-1/800R, it is deduced this region may have some important oncogene/s or other gene/s that play an important role in tumorigenesis. When compared to squamous cell carcinoma data, the duplication observed in the present study is also observed in 28 to 38% of head and neck and also in 25% of cases of untreated malignant lesions of oral squamous cell carcinoma. Thus, this study shows the correlation between in vitro induced squamous cell carcinoma to in vivo tumors.