Diagnosis And Prenatal Diagnosis Of 5 Patients With Particular Chromosomal Abnormalities By Cellular And Molecular Cytogenetic Techniques

Background: The conventional cytogenetic techniques, including chromosome G banding, high-resolution G banding and other banding techniques(such as R banding, Q banding, N banding, C banding and G11 banding etc), have played an important role on chromosome study, and many chromosome syndromes have been identified using these techniques. But all these techniques have their own limitations. For example, these techniques are only fit for the metaphase but the interphase cell, their resolution rate are lower than 3000kb, and many karyotypes with marker chromosome could not be determined.Objective: In order to overcome all the limitations mentioned about, and to achieve genetic eugenics by means of assistant reproductive techniques, this study aimed at developing a fluorescence in situ hybridization-based (FISH-based) molecular cytogenetic technique for detecting minute chromosomal abnormalities, analyzing the relationship between the chromosome abnormalities and clinical manifestations, exploring some forming mechanism of the chromosomal terminal structural abnormality and numerical abnormality so as to confirm and avoid these abnormalities.Methods: G banding, high-resolution G banding, N banding and FISH technology were used for chromosome analysis of five cases with suspected chromosomal abnormalities.Results: The first patient was diagnosed as the chromosome translocation carrier of chromosome 11 and 22, and her 22^nd homologous chromosome satellite increased. Her karyotype was 46, XX, t (11; 22) (q13;q25)dn, 22ps+ mat.ish(11; 22)(RP11-232E17+; RP11-232E17+), excluding a balanced translocation involving the 22nd homologous chromosome. The High-resolution G banding showed a karyotype of 46, XX, del(4)(p15.2;p16.1) for the second patient. The third and fourth patients were diagnosed with the chromosomal chimaera of Turner syndrome and a ring chromosome X by the conventional chromosome analysis and FISH testing, carrying the karyotypes of 45, X [73] /46, X, r(X)(p22q22) [26] and 45, X[71]/46, X, r(X)(p11q21)[29], respectively. The fifth patient's karyotype was 45, X[29]/46, X, idic(Y)(q10)[31].ish(X) (p11.21)(RP11-292J24+),ishidic(Y)(q10)(RP11-115H13×2)(SRY+).Conclusion:1. FISH technology could expand the scope of conventional cytogenetics testing and increase the ability of cytogenetics to identify the chromosomal abnormalities. We precisely characterized a complicated chromosomal abnormality in one patient with overgrowth patients and mental retardation, the ring X chromosomes in two patinets and an abnormal chromosome Y in another patient. Those results have been very helpful for the clinical diagnosis and treatment. 2. FISH technology has many advantages but there are also some limitations. Only directed by conventional karyotype analysis and selected of the corresponding FISH probe, the chromosomal abnormalities could be accurately identified. In this study, we corrected a wrong diagnosis, rescuing the life of a normal fetus successfully through high-resolution G banding and FISH technology.3. FISH technology is a necessary complement to the conventional karyotype analysis, which can not completely replace the conventional karyotype analysis.