B cell hyperactivation in an Ackr4-deficient mouse strain is not caused by lack of ACKR4 expression

TY - JOUR

T1 - B cell hyperactivation in an Ackr4-deficient mouse strain is not caused by lack of ACKR4 expression

AU - Eckert, Nadine

AU - Werth, Kathrin

AU - Willenzon, Stefanie

AU - Tan, Likai

AU - Förster, Reinhold

N1 - ©2019 Society for Leukocyte Biology.

PY - 2020/6

Y1 - 2020/6

N2 - The majority of genetically modified C57BL/6 mice contain congenic passenger DNA around the targeted gene locus as they were generated from 129-derived embryonic stem cells (ESCs) with subsequent backcrossing to the C57BL/6 genetic background. When studying the role of atypical chemokine receptor 4 (ACKR4) in the immune system, we realized that the two available Ackr4-deficient mouse strains (Ackr4-/- and Ackr4GFP/GFP ) show profoundly different phenotypes: Compared to wild-type and Ackr4GFP/GFP mice, Ackr4-/- mice show a strong accumulation of plasma blasts in mesenteric lymph node and spleen as well as increased B cell proliferation after in vitro activation. This phenotype was maintained after further backcrossing to C57BL/6 mice and was even present in heterozygous Ackr4+/- animals, suggesting that a gene variant on the targeted chromosome might cause this phenotype. Exome sequencing revealed that a region of approximately 20 Mbp around the Ackr4 locus on chromosome 9 still originates from the 129 background based on high variant density observed. In activated Ackr4-/- and Ackr4GFP/GFP B cells, transcripts of genes around the Ackr4 locus were equally deregulated compared to C57BL/6 B cells, whereas increased expression of IL-6 was selectively observed in B cells of Ackr4-/- mice. Because the gene encoding for IL-6 is placed on chromosome 5 these findings suggest that passenger DNA around the Ackr4 locus has an indirect effect on B cell activation and IL-6 production. Results of the present study should not only lead to the reinterpretation of data from earlier studies using Ackr4-/- mice but should remind the scientific community about the limitations of mouse models using mice created by gene-targeting of nonsyngeneic ESCs.

AB - The majority of genetically modified C57BL/6 mice contain congenic passenger DNA around the targeted gene locus as they were generated from 129-derived embryonic stem cells (ESCs) with subsequent backcrossing to the C57BL/6 genetic background. When studying the role of atypical chemokine receptor 4 (ACKR4) in the immune system, we realized that the two available Ackr4-deficient mouse strains (Ackr4-/- and Ackr4GFP/GFP ) show profoundly different phenotypes: Compared to wild-type and Ackr4GFP/GFP mice, Ackr4-/- mice show a strong accumulation of plasma blasts in mesenteric lymph node and spleen as well as increased B cell proliferation after in vitro activation. This phenotype was maintained after further backcrossing to C57BL/6 mice and was even present in heterozygous Ackr4+/- animals, suggesting that a gene variant on the targeted chromosome might cause this phenotype. Exome sequencing revealed that a region of approximately 20 Mbp around the Ackr4 locus on chromosome 9 still originates from the 129 background based on high variant density observed. In activated Ackr4-/- and Ackr4GFP/GFP B cells, transcripts of genes around the Ackr4 locus were equally deregulated compared to C57BL/6 B cells, whereas increased expression of IL-6 was selectively observed in B cells of Ackr4-/- mice. Because the gene encoding for IL-6 is placed on chromosome 5 these findings suggest that passenger DNA around the Ackr4 locus has an indirect effect on B cell activation and IL-6 production. Results of the present study should not only lead to the reinterpretation of data from earlier studies using Ackr4-/- mice but should remind the scientific community about the limitations of mouse models using mice created by gene-targeting of nonsyngeneic ESCs.

KW - Animals

KW - B-Lymphocytes/cytology

KW - Cell Proliferation

KW - Chromosomes, Mammalian/immunology

KW - Crosses, Genetic

KW - Embryonic Stem Cells/cytology

KW - Female

KW - Genes, Reporter

KW - Genetic Loci

KW - Green Fluorescent Proteins/genetics

KW - Heterozygote

KW - Homozygote

KW - Interleukin-6/genetics

KW - Lymph Nodes/cytology

KW - Lymphocyte Activation

KW - Male

KW - Mesentery/cytology

KW - Mice

KW - Mice, Inbred C57BL

KW - Mice, Transgenic

KW - Phenotype

KW - Receptors, CCR/deficiency

KW - Spleen/cytology

KW - Whole Exome Sequencing

U2 - 10.1002/JLB.2MA1119-300R

DO - 10.1002/JLB.2MA1119-300R

M3 - SCORING: Journal article

C2 - 31841228

VL - 107

SP - 1155

EP - 1166

JO - J LEUKOCYTE BIOL

JF - J LEUKOCYTE BIOL

SN - 0741-5400

IS - 6

ER -