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Human PMS2 deficiency is associated with impaired immunoglobulin class switch recombination.

Péron S, Metin A, Gardès P, Alyanakian MA, Sheridan E, Kratz CP, Fischer A, Durandy A - J. Exp. Med. (2008)

Bottom Line: In some cases, CSR deficiencies can be associated with abnormal somatic hypermutation.Analysis of CSR deficiencies has helped reveal the key functions of CSR-triggering molecules, i.e., CD40L, CD40, and effector molecules such as activation-induced cytidine deaminase and uracil N-glycosylase.CSR was found partially defective in vivo and markedly impaired in vitro.

View Article: PubMed Central - PubMed

Affiliation: Institut National de Santé et de Recherche Médicale, U768, 75015 Paris, France.

ABSTRACT
Immunoglobulin (Ig) class switch recombination (CSR) deficiencies are rare primary immunodeficiencies characterized by the lack of switched isotype (IgG/IgA/IgE) production. In some cases, CSR deficiencies can be associated with abnormal somatic hypermutation. Analysis of CSR deficiencies has helped reveal the key functions of CSR-triggering molecules, i.e., CD40L, CD40, and effector molecules such as activation-induced cytidine deaminase and uracil N-glycosylase. We report a new form of B cell-intrinsic CSR deficiency found in three patients with deleterious, homozygous mutations in the gene encoding the PMS2 component of the mismatch repair machinery. CSR was found partially defective in vivo and markedly impaired in vitro. It is characterized by the defective occurrence of double-strand DNA breaks (DSBs) in switch regions and abnormal formation of switch junctions. This observation strongly suggests a role for PMS2 in CSR-induced DSB generation.

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Defective DSB occurrence and junction repair. (A) DSB occurrence in the Sμ regions of DNA agarose plugs from 20,000 B cells (CD19+) or non–B cells (CD19−) were treated or not with T4 polymerase. After ligation with the linker, ligation-mediated PCR products were transferred and Southern blotting performed using a 32P-labeled Sμ probe. DSBs were detected in the Sμ regions of control (n = 4) but not of P1 (n = 1) B cells. Amplification of Pinx1 was used as a control of DNA integrity and input. (B) Abnormal pattern of Sμ–Sα1 junctions in patients. Representation of the length of the switch junctions is shown (controls, n = 38; P1, n = 29; P2, n = 16; and P3, n = 15). Statistically significant differences are indicated (*, P < 0.05; and ***, P < 0.001 using the χ2 test).
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fig4: Defective DSB occurrence and junction repair. (A) DSB occurrence in the Sμ regions of DNA agarose plugs from 20,000 B cells (CD19+) or non–B cells (CD19−) were treated or not with T4 polymerase. After ligation with the linker, ligation-mediated PCR products were transferred and Southern blotting performed using a 32P-labeled Sμ probe. DSBs were detected in the Sμ regions of control (n = 4) but not of P1 (n = 1) B cells. Amplification of Pinx1 was used as a control of DNA integrity and input. (B) Abnormal pattern of Sμ–Sα1 junctions in patients. Representation of the length of the switch junctions is shown (controls, n = 38; P1, n = 29; P2, n = 16; and P3, n = 15). Statistically significant differences are indicated (*, P < 0.05; and ***, P < 0.001 using the χ2 test).

Mentions: As an attempt to localize the precise step of the CSR defect, we checked for the occurrence of DSBs in Sμ regions of sCD40L plus IL-4–activated P1 B cells. Sμ DSBs could not be detected, even in the presence of T4 polymerase, suggesting a defect in the generation of both scattered and blunt DSBs (Fig. 4 A). One cannot formally exclude that DSBs were not detected because of the low number of available B cells; nevertheless, our data indicate that Sμ DSB generation was at least markedly decreased in PMS2-deficient B cells as compared with controls.


Human PMS2 deficiency is associated with impaired immunoglobulin class switch recombination.

Péron S, Metin A, Gardès P, Alyanakian MA, Sheridan E, Kratz CP, Fischer A, Durandy A - J. Exp. Med. (2008)

Defective DSB occurrence and junction repair. (A) DSB occurrence in the Sμ regions of DNA agarose plugs from 20,000 B cells (CD19+) or non–B cells (CD19−) were treated or not with T4 polymerase. After ligation with the linker, ligation-mediated PCR products were transferred and Southern blotting performed using a 32P-labeled Sμ probe. DSBs were detected in the Sμ regions of control (n = 4) but not of P1 (n = 1) B cells. Amplification of Pinx1 was used as a control of DNA integrity and input. (B) Abnormal pattern of Sμ–Sα1 junctions in patients. Representation of the length of the switch junctions is shown (controls, n = 38; P1, n = 29; P2, n = 16; and P3, n = 15). Statistically significant differences are indicated (*, P < 0.05; and ***, P < 0.001 using the χ2 test).
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Related In: Results  -  Collection

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fig4: Defective DSB occurrence and junction repair. (A) DSB occurrence in the Sμ regions of DNA agarose plugs from 20,000 B cells (CD19+) or non–B cells (CD19−) were treated or not with T4 polymerase. After ligation with the linker, ligation-mediated PCR products were transferred and Southern blotting performed using a 32P-labeled Sμ probe. DSBs were detected in the Sμ regions of control (n = 4) but not of P1 (n = 1) B cells. Amplification of Pinx1 was used as a control of DNA integrity and input. (B) Abnormal pattern of Sμ–Sα1 junctions in patients. Representation of the length of the switch junctions is shown (controls, n = 38; P1, n = 29; P2, n = 16; and P3, n = 15). Statistically significant differences are indicated (*, P < 0.05; and ***, P < 0.001 using the χ2 test).
Mentions: As an attempt to localize the precise step of the CSR defect, we checked for the occurrence of DSBs in Sμ regions of sCD40L plus IL-4–activated P1 B cells. Sμ DSBs could not be detected, even in the presence of T4 polymerase, suggesting a defect in the generation of both scattered and blunt DSBs (Fig. 4 A). One cannot formally exclude that DSBs were not detected because of the low number of available B cells; nevertheless, our data indicate that Sμ DSB generation was at least markedly decreased in PMS2-deficient B cells as compared with controls.

Bottom Line: In some cases, CSR deficiencies can be associated with abnormal somatic hypermutation.Analysis of CSR deficiencies has helped reveal the key functions of CSR-triggering molecules, i.e., CD40L, CD40, and effector molecules such as activation-induced cytidine deaminase and uracil N-glycosylase.CSR was found partially defective in vivo and markedly impaired in vitro.

View Article: PubMed Central - PubMed

Affiliation: Institut National de Santé et de Recherche Médicale, U768, 75015 Paris, France.

ABSTRACT
Immunoglobulin (Ig) class switch recombination (CSR) deficiencies are rare primary immunodeficiencies characterized by the lack of switched isotype (IgG/IgA/IgE) production. In some cases, CSR deficiencies can be associated with abnormal somatic hypermutation. Analysis of CSR deficiencies has helped reveal the key functions of CSR-triggering molecules, i.e., CD40L, CD40, and effector molecules such as activation-induced cytidine deaminase and uracil N-glycosylase. We report a new form of B cell-intrinsic CSR deficiency found in three patients with deleterious, homozygous mutations in the gene encoding the PMS2 component of the mismatch repair machinery. CSR was found partially defective in vivo and markedly impaired in vitro. It is characterized by the defective occurrence of double-strand DNA breaks (DSBs) in switch regions and abnormal formation of switch junctions. This observation strongly suggests a role for PMS2 in CSR-induced DSB generation.

Show MeSH
Related in: MedlinePlus