Leaky severe combined immunodeficiency in mice lacking non-homologous end joining factors XLF and MRI

10.1101/2020.03.04.976829 ◽

2020 ◽

Author(s):

Sergio Castañeda-Zegarra ◽

Qindong Zhang ◽

Amin Alirezaylavasani ◽

Marion Fernandez-Berrocal ◽

Rouan Yao ◽

...

Keyword(s):

Severe Combined Immunodeficiency ◽

Embryonic Lethality ◽

Combined Immunodeficiency ◽

End Joining ◽

Mild Phenotype ◽

Reduced Body ◽

Non Homologous End Joining ◽

Mature Lymphocyte ◽

And Function

AbstractNon-homologous end-joining (NHEJ) is a DNA repair pathway required to detect, process, and ligate DNA double-stranded breaks (DSBs) throughout the cell cycle. The NHEJ pathway is necessary for V(D)J recombination in developing B and T lymphocytes. During NHEJ, Ku70 and Ku80 form a heterodimer that recognizes DSBs and promotes recruitment and function of downstream factors PAXX, MRI, DNA-PKcs, Artemis, XLF, XRCC4, and LIG4. Mutations in several known NHEJ genes result in severe combined immunodeficiency (SCID). Inactivation of Mri, Paxx or Xlf in mice results in normal or mild phenotype, while combined inactivation of Xlf/Mri, Xlf/Paxx, or Xlf/Dna-pkcs leads to late embryonic lethality. Here, we describe three new mouse models. We demonstrate that deletion of Trp53 rescues embryonic lethality in mice with combined deficiencies of Xlf and Mri. Furthermore, Xlf-/-Mri-/-Trp53+/- and Xlf-/-Paxx-/-Trp53+/- mice possess reduced body weight, severely reduced mature lymphocyte counts, and accumulation of progenitor B cells. We also report that combined inactivation of Mri/Paxx results in live-born mice with modest phenotype, and combined inactivation of Mri/Dna-pkcs results in embryonic lethality. Therefore, we conclude that XLF is functionally redundant with MRI and PAXX during lymphocyte development in vivo. Moreover, Mri genetically interacts with Dna-pkcs and Paxx.

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Leaky Severe Combined Immunodeficiency in Mice Lacking Non-homologous End Joining Factors XLF and MRI

10.20944/preprints202009.0145.v1 ◽

2020 ◽

Author(s):

Sergio Castaneda-Zegarra ◽

Qindong Zhang ◽

Amin Alirezaylavasani ◽

Marion Fernandez-Berrocal ◽

Rouan Yao ◽

...

Keyword(s):

Severe Combined Immunodeficiency ◽

Embryonic Lethality ◽

Combined Immunodeficiency ◽

End Joining ◽

Mild Phenotype ◽

Reduced Body ◽

Non Homologous End Joining ◽

Mature Lymphocyte ◽

And Function

Non-homologous end-joining (NHEJ) is a DNA repair pathway required to detect, process, and ligate DNA double-stranded breaks (DSBs) throughout the cell cycle. The NHEJ pathway is necessary for V(D)J recombination in developing B and T lymphocytes. During NHEJ, Ku70 and Ku80 form a heterodimer that recognizes DSBs and promotes recruitment and function of downstream factors PAXX, MRI, DNA-PKcs, Artemis, XLF, XRCC4, and LIG4. Mutations in several known NHEJ genes result in severe combined immunodeficiency (SCID). Inactivation of Mri, Paxx or Xlf in mice results in normal or mild phenotype, while combined inactivation of Xlf/Mri, Xlf/Paxx, or Xlf/Dna-pkcs leads to late embryonic lethality. Here, we describe three new mouse models. We demonstrate that deletion of Trp53 rescues embryonic lethality in mice with combined deficiencies of Xlf and Mri. Furthermore, Xlf-/-Mri-/-Trp53+/- and Xlf-/-Paxx-/-Trp53+/- mice possess reduced body weight, severely reduced mature lymphocyte counts, and accumulation of progenitor B cells. We also report that combined inactivation of Mri/Paxx results in live-born mice with modest phenotype, and combined inactivation of Mri/Dna-pkcs results in embryonic lethality. Therefore, we conclude that XLF is functionally redundant with MRI and PAXX during lymphocyte development in vivo. Moreover, Mri genetically interacts with Dna-pkcs and Paxx.

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Deletion of Ku70, Ku80, or Both Causes Early Aging without Substantially Increased Cancer

Molecular and Cellular Biology ◽

10.1128/mcb.00785-07 ◽

2007 ◽

Vol 27 (23) ◽

pp. 8205-8214 ◽

Cited By ~ 85

Author(s):

Han Li ◽

Hannes Vogel ◽

Valerie B. Holcomb ◽

Yansong Gu ◽

Paul Hasty

Keyword(s):

Genetic Background ◽

Double Mutant ◽

Severe Combined Immunodeficiency ◽

Nonhomologous End Joining ◽

Mutant Mice ◽

Combined Immunodeficiency ◽

End Joining ◽

High Incidence ◽

Early Aging ◽

Increased Sensitivity

ABSTRACT Ku70 forms a heterodimer with Ku80, called Ku, that is critical for repairing DNA double-stand breaks by nonhomologous end joining and for maintaining telomeres. Mice with either gene mutated exhibit similar phenotypes that include increased sensitivity to ionizing radiation and severe combined immunodeficiency. However, there are also differences in the reported phenotypes. For example, only Ku70 mutants are reported to exhibit a high incidence of thymic lymphomas while only Ku80 mutants are reported to exhibit early aging with very low cancer levels. There are two explanations for these differences. First, either Ku70 or Ku80 functions outside the Ku heterodimer such that deletion of one is not identical to deletion of the other. Second, divergent genetic backgrounds or environments influence the phenotype. To distinguish between these possibilities, the Ku70 and Ku80 mutations were crossed together to generate Ku70, Ku80, and double-mutant mice in the same genetic background raised in the same environment. We show that these three cohorts have similar phenotypes that most resemble the previous report for Ku80 mutant mice, i.e., early aging without substantially increased cancer levels. Thus, our observations suggest that the Ku heterodimer is important for longevity assurance in mice since divergent genetic backgrounds and/or environments likely account for these previously reported differences.

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