Farizan, Ahmad
(2008)
Analysis of p27 and cyclin 01 genes in
gliomas and meningiomas using
molecular genetic,
immunohistochemical and immunogold
electron microscopic techniques.
Masters thesis, Pusat Pengajian Sains Perubatan.
Abstract
Meningiomas and gliomas are two most commonly reported brain tumor cases
worldwide. These types of tumors might occur due to the disruption of the normal cell
cycle which is highly controlled by p27 and cyclin 01 genes. This study was performed
to determine the mutational status of p27 and cyclin D1, level of both protein expression
and the localization of both proteins at ultrastructural level via analyses of molecular
genetic, immunohistochemistry and immunogold electron microscopy respectively. The
molecular genetic analysis revealed mutations in exon 4 of cyclin 01 gene but none was
detected in other studied regions of exon 5 of cyclin 01 gene and exon 1 and 2 of p27
gene. Five different mutations were detected in 2 glioma (8.0%) and 3 meningioma
(11.5%) samples. DNA sequencing for the two gliomas samples revealed the presence
of non-sense mutation which resulted to the change of C toT nucleotide at codon 223
(Lys223Lys). In the first glioma sample, we also detected a G base deletion at codon
214 which caused a frameshift mutation (Pro214Arg). In addition to that, we also found
two other missense mutations in the second glioma sample. T to C nucleotide changes
were detected at codon 215 and codon 217 which caused aspartic acid to Glycine
changes in two different loci. Screening of mutations in meningiomas cases revealed 3
cases of non-sense mutations and 3 cases of missense mutations in a total of 3
samples. In all 3 samples, we found 3 cases of C to T nucleotide change which resulted
to non-sense mutations at codon 223 (Lys223Lys). In the second and third meningioma
samples, we found an additional of T to C nucleotide changes at codon 215 which
caused missense mutations (Asp215Giy). Another missense mutation was found at
codon 217 which showed T to C nucleotide change in the third meningioma sample. Immunohistochemistry analysis of the same group of samples revealed p27 protein
overexpression in all cases including meningiomas (82.6%), low grades gliomas (80.0%)
and high grades gliomas (84.6%). We subsequently found high level of cyclin 01
expression in meningiomas (70.8%), equal expression of cyclin 01 in low grades of
gliomas (50% are low expressers and 50% are high expressers), and downregulation of
the protein in higher grades of gliomas (76.9% were low expressers). lmmunogold
electron microscopy analysis of cyclin 01 and p27 proteins showed that both proteins
were found to be localized at cytoplasm and nucleus of the cells. Our statistical analysis
gave no significant correlation between the presence of cyclin 01 mutations with the
downregulation of the protein in both meningiomas (p=0.616) and gliomas (p=0.905).
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