Other Cytogenetic techniques include Fluorescent in-situ hybridization, Centromere or C-banding, replication banding, Sub-microscopic telomere analysis, distamycin staining and Comparative Genomic Hybridization (1). Abnormalities in chromosomes can also be identified by non-cytogenetic methods, like that of Microarray analysis and Molecular analysis of Telomeric sequences (1). Human numerical abnormalities are now measured by the advent of cytogenetics, which include Downs Syndrome, Turners syndrome and Klinefelters syndrome. The advance of molecular cytogenetics started in 1980s with the advent of Fluorescent in-situ hybridization. Later than FISH, technique of chromosome microdissection came in picture in which micromanipulation and examination of chromosome was carried out. This method lead to study in detail the aberration in chromosomal structure that could be isolated cloned and thereby studied in even finer detail. This method is also been put to medical use like in diagnosis of cancer and in hematological malignancies where it is used to determine the chromosomal translocations in the malignant cells, thus making the diagnosis easier and thereby the treatment becomes more specific. It is also used in the identification of the abnormality in myeloid leukemia (2). The future focuses on molecular cytogenetics include Comparative genomic hybridization microarrays; Single-Polynucleotide based Polymerization based karyotyping.
Report for the clinician referred to:
1. Observation and background:
Given sample of Mrs. Krerr has been analyzed and karyotyping was carried out based on the G-banding Karyotype. There were clear indications of translocation between in Chromosome 4 and 11 having t(4;11)(q21:p13) phenotype. Based on published literature and reports translocation in chromosome 4; 11 was found to be associated with high risk infant acute leukemia (3) which arises due to illegitimate re-combination between MLL and AF4 gene. Identification of this gene translocation in early stage of life cycle allows us to define the treatment regime in subsequent development of diseases (4). The mechanistic aspect of this translocation is largely unknown but researchers are able to map the genomic breakpoints and, in this particular case it was found to be hyper-sensitive to Dnase I and the cleavage site for Topoisomerase II.
2. Probable Gene involved and proteins:
a) AF4p12, also known as FRYL gene homologous to Drosophila FRY gene could be involved in maintaining integrity of polarized cell during morphogenesis (6).
b) MLL 11 Q23 transcriptional regulators.
3. Further investigations:
Observed karyotype and interpretation needs to be validated based on little more cytogenetic analysis including Q- banding to obtain high resolution banding pattern to locate precise translocation. Similarly NOR (Silver) staining will help to identify translocation due to involvement of shorter arm translocation in given sample. But it is highly recommended to use Q-PCR methodology using fusion specific primer (i.e. primer which amplifies fusion region of MLL and AF4). The results of PCR amplification can