Absence of Pericentromeric Heterochromatin (9qh-) in a Patient with Bilateral Retinoblastoma

Abstract

The polymorphisms of constitutive heterochromatin regions, present on chromosomes 1, 9, 16 and Y, are inherited in a Mendelian fashion. The C-band heteromorphism has been reported to be associated with various types of cancer. Heterochromatin is considered to play a role in protecting genome against the mutagens. Changes in the quantity and proportion of the different types of satellite DNA might increase the genetic susceptibility in people with heterochromatic variations, which in turn cause chromosome instability and predispose the individual to cancer. We report a case of bilateral retinoblastoma with complete absence of pericentromeric heterochromatin on one of the chromosomes number 9. A similar deficiency of pericentromeric heterochromatin on chromosome number 9 and 16 has been reported in a phenotypically normal individual and a Down syndrome case, respectively. This deficiency was found to be inherited from the father in all the three cases. Complete absence of pericentromeric heterochromatin of chromosome 9 is not being reported in association with cancer syndromes. Further studies are necessary to understand the role of this factor in normals and in those with cancer susceptibility, specially with retinoblastoma and the paternal origin of this deficiency.

Caudal dysplasia sequence with penile enlargement: Case report and a potential pathogenic hypothesis

“…The deletion of the heterochromatin region of the Y chromosome that was detected in our neonate by CGH is a well‐known phenomenon of polymorphism of the human Y chromosome, which does not adversely affect development or spermatogenesis [Lau and Schonberg, 1984; Nazarenko et al, 1987; Sivakumaran et al, 1997]. Unfortunately, the father did not consent to genetic studies to verify the presence of a similar deletion in his Y chromosome.…”

pRb2/p130: a new candidate for retinoblastoma tumor formation

“…Additional genetic alterations, such as monosomy 16 or del(16q) (Pogosianz and Kuznetsova, 1986;Oliveros and Yunis, 1995), monosomy 17 or del(17p), i(17p) (Squire et al, 1984;Oliveros and Yunis, 1995), complete absence of pericentromeric heterochromatin on chromosome 9 (Sivakumaran et al, 1997) and loss of X or Y sex chromosomes (Pogosianz and Kuznetsova, 1986) have also been described. The presence of abnormal gene amplifications has also been discovered in retinoblastoma (Lee et al, 1984;Arheden et al, 1988;Imbert et al, 2001;Chen et al, 2002).…”

The role of α-satellite DNA and heterochromatin polymorphism in leukemia patients and illicit drug addicts

“…Changes in the quantity and proportion of the different types of satellite DNA may increase genetic susceptibility in people with heterochromatin variations, which in turn cause chromosome instability and predispose the individual to cancers and malignancies (Sivakumaran et al, 1997). Various surveys have shown an increased frequency of heterochromatin polymorphisms in patients with different disorders, suggesting their possible role in the development of neoplasia (Atkin and Brito-Babapulle, 1981;Ranni et al, 1987).…”

“…A number of reports have indicated pronounced heteromorphism in size and localization in the C-band region of chromosome 1, 9 and 16 in individuals with different malignancies, such as polycythemia vera (Atkin and Brito-Babapulle, 1981;Ranni et al, 1987), male infertility (Madon et al, 2005), ataxia telangiectasia (Grewal and Moazed, 2003), various types of leukemias (Rivera et al, 1999;Enukashvily et al, 2007), and cancers such as breast cancer (Berger et al, 1985;Tsezou et al, 1993;Tsuda et al, 2002;Plohl et al, 2008), retinoblastoma (Sivakumaran et al, 1997), and colon carcinoma (Neglia et al, 2003).…”

“…Different important functions have been ascribed to satellite DNA, from the imperative centromeric function in mitosis and meiosis to the recent discovery of its involvement in regulatory functions via satellite transcripts. Moreover, satellite DNAs, among other repetitive sequences, are believed to be the "engine" triggering the mammalian genome (Sivakumaran et al, 1997;Grewal and Moazed, 2003). Heterochromatin mediates many diverse functions in the cell nucleus, including centromere function, gene silencing, regulation of gene expression, and nuclear organization (Cortés et al, 2003).…”