Ataxia telangiectasia mutated (ATM) and mutS homologue 2 (MSH2) are important DNA repair proteins that participate in DNA repair pathways to maintain genomic integrity. Mice deficient for ATM and MSH2 mice are viable. However, ATM-/- mice show growth retardation, neurological defects, and spontaneous lymphomagenesis. MSH2-/- mice suffer from aggressive lymphoid tumors between two to five months of age and have increased microsatellite instability, which predisposes MSH2-/- mice to carcinomas. However, mice deficient in both ATM and MSH2 are unable to survive beyond postnatal day 21 (P21). The observed lethality in ATM-/-MSH2-/- mice may result from the accumulation of genomic instability. To address this hypothesis, metaphase spreads were examined for chromosomal aberrations in B cells, which undergo genetically programmed DNA recombination and mutation. To bypass the lethality in ATM-/-MSH2-/- mice, a conditional knockout of ATM was bred onto an MSH2-/- background strain to generate CD21cre+ATMF/FMSH2-/- mice, which are referred to as ATM∆/∆MSH2-/-. In these mice, Cre expression, which is regulated by the CD21 promoter, deletes floxed ATM alleles in naïve mature MSH2-/- B-cells. ATM∆/∆ B-cells showed low levels of chromosomal aberrations whereas ATM∆/∆MSH2-/-B-cells had levels of chromosomal aberrations that was comparable to MSH2-/- B-cells. The latter result suggested that ATM was incompletely deleted in ATM∆/∆ B-cells. Analysis of ATM∆/∆ B cell lysates showed residual ATM protein that may account for the comparable chromosomal aberrations in ATM∆/∆MSH2-/-and MSH2-/- metaphase spreads. ATM-/-MSH2-/- embryos die in utero at approximately E16-E20. Thus, mouse embryonic fibroblasts (MEFs) were isolated from E13.5-15.5 ATM-/-MSH2-/- embryos and examined for chromosomal aberrations. The ATM-/-MSH2-/- MEF metaphase spreads displayed a similar pattern of chromosomal aberrations as ATM-/- MEFs, which does not support the hypothesis that ATM-/-MSH2-/- mice die from increased genomic instability; however, additional metaphase analyses are required to conclusively determine whether genomic instability does or does not impair ATM-/-MSH2-/- embryonic development.
","abstract_html":"<p>Ataxia telangiectasia mutated (ATM) and mutS homologue 2 (MSH2) are important DNA repair proteins that participate in DNA repair pathways to maintain genomic integrity. Mice deficient for ATM and MSH2 mice are viable. However, <em>ATM<sup>-/-</sup></em> mice show growth retardation, neurological defects, and spontaneous lymphomagenesis. <em>MSH2<sup>-/-</sup></em> mice suffer from aggressive lymphoid tumors between two to five months of age and have increased microsatellite instability, which predisposes <em>MSH2<sup>-/-</sup></em> mice to carcinomas. However, mice deficient in both ATM and MSH2 are unable to survive beyond postnatal day 21 (P21). The observed lethality in <em>ATM<sup>-/-</sup>MSH2<sup>-/-</sup></em> mice may result from the accumulation of genomic instability. To address this hypothesis, metaphase spreads were examined for chromosomal aberrations in B cells, which undergo genetically programmed DNA recombination and mutation. To bypass the lethality in <em>ATM<sup>-/-</sup>MSH2<sup>-/-</sup> </em>mice, a conditional knockout of ATM was bred onto an <em>MSH2<sup>-/-</sup></em> background strain to generate <em>CD21cre<sup>+</sup>ATM<sup>F/F</sup>MSH2<sup>-/-</sup></em> mice, which are referred to as <em>ATM</em><em><sup>∆/∆</sup></em><em>MSH2<sup>-/-</sup></em>. In these mice, <em>Cre</em> expression, which is regulated by the CD21 promoter, deletes floxed <em>ATM</em> alleles in naïve mature <em>MSH2<sup>-/-</sup></em> B-cells. <em>ATM</em><em><sup>∆/∆</sup></em> B-cells showed low levels of chromosomal aberrations whereas <em>ATM</em><em><sup>∆/∆</sup></em><em>MSH2<sup>-/-</sup></em>B-cells had levels of chromosomal aberrations that was comparable to <em>MSH2<sup>-/-</sup></em> B-cells. The latter result suggested that ATM was incompletely deleted in <em>ATM</em><em><sup>∆/∆</sup></em><em> </em>B-cells. Analysis of <em>ATM</em><em><sup>∆/∆</sup></em><em> </em>B cell lysates showed residual ATM protein that may account for the comparable chromosomal aberrations in <em>ATM</em><em><sup>∆/∆</sup></em><em>MSH2<sup>-/-</sup></em>and <em>MSH2<sup>-/- </sup></em>metaphase spreads. <em>ATM<sup>-/-</sup>MSH2<sup>-/-</sup></em> embryos die <em>in utero</em> at approximately E16-E20. Thus, mouse embryonic fibroblasts (MEFs) were isolated from E13.5-15.5 <em>ATM<sup>-/-</sup>MSH2<sup>-/-</sup></em> embryos and examined for chromosomal aberrations. The <em>ATM<sup>-/-</sup>MSH2<sup>-/-</sup></em> MEF metaphase spreads displayed a similar pattern of chromosomal aberrations as <em>ATM<sup>-/-</sup></em> MEFs, which does not support the hypothesis that<em> ATM<sup>-/-</sup>MSH2<sup>-/-</sup></em> mice die from increased genomic instability; however, additional metaphase analyses are required to conclusively determine whether genomic instability does or does not impair <em>ATM<sup>-/-</sup>MSH2<sup>-/-</sup></em> embryonic development.</p>","abstract_has_math":false,"creators":["Inalman, Yeliz"],"institution":null,"degree_name":"Master of Science (M.S.)","degree_level":"Thesis","degree_discipline":"Biology","degree_department":null,"school":null,"contributors":["Bao Q. Vuong","Karen Hubbard","Shireen Saleque"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2019,"date_issued":"2019-01-01T08:00:00Z","date_published":"2019-01-01T08:00:00Z","updated_at":"2026-07-24T01:57:21Z","subjects":["Class switch recombination","metaphase spreads","B-cells","MEFs","DNA repair","genomic instability","Cancer Biology","Cell Biology","Developmental Biology","Immunopathology","Molecular Biology","Molecular Genetics"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://academicworks.cuny.edu/cc_etds_theses/778","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Bao Q. Vuong","Karen Hubbard","Shireen Saleque"]},{"key":"dc:creator","label":"Author","values":["Inalman, Yeliz"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2024-06-05T07:00:00Z"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Biology"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science (M.S.)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Class switch recombination","metaphase spreads","B-cells","MEFs","DNA repair","genomic instability","Cancer Biology","Cell Biology","Developmental Biology","Immunopathology","Molecular Biology","Molecular Genetics"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://academicworks.cuny.edu/cc_etds_theses/778"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Ataxia telangiectasia mutated (ATM) and mutS homologue 2 (MSH2) are important DNA repair proteins that participate in DNA repair pathways to maintain genomic integrity. Mice deficient for ATM and MSH2 mice are viable. However, ATM-/- mice show growth retardation, neurological defects, and spontaneous lymphomagenesis. MSH2-/- mice suffer from aggressive lymphoid tumors between two to five months of age and have increased microsatellite instability, which predisposes MSH2-/- mice to carcinomas. However, mice deficient in both ATM and MSH2 are unable to survive beyond postnatal day 21 (P21). The observed lethality in ATM-/-MSH2-/- mice may result from the accumulation of genomic instability. To address this hypothesis, metaphase spreads were examined for chromosomal aberrations in B cells, which undergo genetically programmed DNA recombination and mutation. To bypass the lethality in ATM-/-MSH2-/- mice, a conditional knockout of ATM was bred onto an MSH2-/- background strain to generate CD21cre+ATMF/FMSH2-/- mice, which are referred to as ATM∆/∆MSH2-/-. In these mice, Cre expression, which is regulated by the CD21 promoter, deletes floxed ATM alleles in naïve mature MSH2-/- B-cells. ATM∆/∆ B-cells showed low levels of chromosomal aberrations whereas ATM∆/∆MSH2-/-B-cells had levels of chromosomal aberrations that was comparable to MSH2-/- B-cells. The latter result suggested that ATM was incompletely deleted in ATM∆/∆ B-cells. Analysis of ATM∆/∆ B cell lysates showed residual ATM protein that may account for the comparable chromosomal aberrations in ATM∆/∆MSH2-/-and MSH2-/- metaphase spreads. ATM-/-MSH2-/- embryos die in utero at approximately E16-E20. Thus, mouse embryonic fibroblasts (MEFs) were isolated from E13.5-15.5 ATM-/-MSH2-/- embryos and examined for chromosomal aberrations. The ATM-/-MSH2-/- MEF metaphase spreads displayed a similar pattern of chromosomal aberrations as ATM-/- MEFs, which does not support the hypothesis that ATM-/-MSH2-/- mice die from increased genomic instability; however, additional metaphase analyses are required to conclusively determine whether genomic instability does or does not impair ATM-/-MSH2-/- embryonic development.
"]},{"key":"dc:title","label":"Title","values":["Characterizing Chromosomal Aberrations in Cells Deficient for Both ATM and MSH2"]}]}],"canonical_facts":{"dc:contributor":["Bao Q. Vuong","Karen Hubbard","Shireen Saleque"],"dc:creator":["Inalman, Yeliz"],"dc:date.available":["2024-06-05T07:00:00Z"],"dc:description.abstract":["Ataxia telangiectasia mutated (ATM) and mutS homologue 2 (MSH2) are important DNA repair proteins that participate in DNA repair pathways to maintain genomic integrity. Mice deficient for ATM and MSH2 mice are viable. However, ATM-/- mice show growth retardation, neurological defects, and spontaneous lymphomagenesis. MSH2-/- mice suffer from aggressive lymphoid tumors between two to five months of age and have increased microsatellite instability, which predisposes MSH2-/- mice to carcinomas. However, mice deficient in both ATM and MSH2 are unable to survive beyond postnatal day 21 (P21). The observed lethality in ATM-/-MSH2-/- mice may result from the accumulation of genomic instability. To address this hypothesis, metaphase spreads were examined for chromosomal aberrations in B cells, which undergo genetically programmed DNA recombination and mutation. To bypass the lethality in ATM-/-MSH2-/- mice, a conditional knockout of ATM was bred onto an MSH2-/- background strain to generate CD21cre+ATMF/FMSH2-/- mice, which are referred to as ATM∆/∆MSH2-/-. In these mice, Cre expression, which is regulated by the CD21 promoter, deletes floxed ATM alleles in naïve mature MSH2-/- B-cells. ATM∆/∆ B-cells showed low levels of chromosomal aberrations whereas ATM∆/∆MSH2-/-B-cells had levels of chromosomal aberrations that was comparable to MSH2-/- B-cells. The latter result suggested that ATM was incompletely deleted in ATM∆/∆ B-cells. Analysis of ATM∆/∆ B cell lysates showed residual ATM protein that may account for the comparable chromosomal aberrations in ATM∆/∆MSH2-/-and MSH2-/- metaphase spreads. ATM-/-MSH2-/- embryos die in utero at approximately E16-E20. Thus, mouse embryonic fibroblasts (MEFs) were isolated from E13.5-15.5 ATM-/-MSH2-/- embryos and examined for chromosomal aberrations. The ATM-/-MSH2-/- MEF metaphase spreads displayed a similar pattern of chromosomal aberrations as ATM-/- MEFs, which does not support the hypothesis that ATM-/-MSH2-/- mice die from increased genomic instability; however, additional metaphase analyses are required to conclusively determine whether genomic instability does or does not impair ATM-/-MSH2-/- embryonic development.
"],"dc:identifier":["https://academicworks.cuny.edu/cc_etds_theses/778"],"dc:subject":["Class switch recombination","metaphase spreads","B-cells","MEFs","DNA repair","genomic instability","Cancer Biology","Cell Biology","Developmental Biology","Immunopathology","Molecular Biology","Molecular Genetics"],"dc:title":["Characterizing Chromosomal Aberrations in Cells Deficient for Both ATM and MSH2"],"thesis:degree_discipline":["Biology"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["Master of Science (M.S.)"]},"updated_at":"2026-07-24T01:57:21Z"}