ACK1 and BRK non-receptor tyrosine kinase deficiencies are associated with familial systemic lupus and involved in efferocytosis

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    The paper reports rare compound heterozygous deletion variants that affect the kinase domains of non-receptor tyrosine kinases TNK and ACK1 in families with human systemic lupus erythematosus (SLE). Using a mouse experimental model and human induced pluripotent stem cell (hiPSC)-derived macrophages, the study provides solid evidence that clarifies cause-effect relationships and that suggests a potential cellular mechanism underlying the resultant nephritis. With the identification of novel SLE-related genes, this manuscript provides an important basis for understanding the molecular and cellular basis of SLE pathogenesis.

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Abstract

Systemic Lupus Erythematosus (SLE) is an autoimmune disease, the pathophysiology and genetic basis of which are incompletely understood. Non-receptor tyrosine kinases (NRTKs) regulate activation, migration, and proliferation of immune cells. We report compound heterozygous deleterious variants in the kinase domains of the non-receptor tyrosine kinases (NRTK) TNK2/ACK1 in one multiplex family and PTK6/BRK in another. Experimental blockade of mouse ACK1 or BRK increases glomerular IgG deposits and circulating autoantibodies in an in vivo SLE model. In addition, we found that the patients’ ACK and BRK variants impair efferocytosis, the MERTK-mediated anti-inflammatory response to apoptotic cells, in human induced Pluripotent Stem Cells (hiPSC)-derived macrophages. Overall, our data suggest that ACK1 and BRK deficiencies are associated with human SLE and impair efferocytosis. Human ACK1 and BRK kinases loss of function variants underlie systemic lupus erythematosus in young patients from multiplex families and disrupt the anti-inflammatory response of macrophages to apoptotic cells.

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  1. eLife assessment

    The paper reports rare compound heterozygous deletion variants that affect the kinase domains of non-receptor tyrosine kinases TNK and ACK1 in families with human systemic lupus erythematosus (SLE). Using a mouse experimental model and human induced pluripotent stem cell (hiPSC)-derived macrophages, the study provides solid evidence that clarifies cause-effect relationships and that suggests a potential cellular mechanism underlying the resultant nephritis. With the identification of novel SLE-related genes, this manuscript provides an important basis for understanding the molecular and cellular basis of SLE pathogenesis.

  2. Reviewer #1 (Public Review):

    Summary:

    The authors report compound heterozygous deleterious variants in the kinase domains of the non-receptor tyrosine kinases (NRTK) TNK2/ACK1 in familial SLE. They suggest that ACK1 and BRK deficiencies are associated with human SLE and impair efferocytosis.

    Strengths:

    The identification of similar mutations in non-receptor tyrosine kinases (NRTKs) in two different families with familial SLE is a significant finding in human disease. Furthermore, the paper provides a detailed analysis of the molecular mechanisms behind the impairment of efferocytosis caused by mutations in ACK1 and BRK.

    Weaknesses:

    A critical point in this paper is whether the loss of function of ACK1 or BRK contributes to the onset of familial SLE. The authors emphasize that inhibitors of ACK1/BRK worsened IgG deposition in the kidneys in a pristane-induced SLE model, which contributes not to the onset but to the exacerbation of SLE, thus only partially supporting their claim.

  3. Reviewer #2 (Public Review):

    Summary:

    In this manuscript, the authors revealed that genetic deficiencies of ACK1 and BRK are associated with human SLE. First, the authors found that compound heterozygous deleterious variants in the kinase domains of the non-receptor tyrosine kinases (NRTK) TNK2/ACK1 in one multiplex family and PTK6/BRK in another family. Then, by an experimental blockade of ACK1 or BRK in a mouse SLE model, they found an increase in glomerular IgG deposits and circulating autoantibodies. Furthermore, they reported that ACK and BRK variants from the SLE patients impaired the MERTK-mediated anti-inflammatory response to apoptotic cells in human induced pluripotent stem cells (hiPSC)-derived macrophages. This work identified new SLE-associated ACK and BRK variants and a role for the NRTK TNK2/ACK1 and PTK6/BRK in efferocytosis, providing a new molecular and cellular mechanism of SLE pathogenesis.

    Strengths:

    This work identified new SLE-associated ACK and BRK variants and a role for the NRTK TNK2/ACK1 and PTK6/BRK in efferocytosis, providing a new molecular and cellular mechanism of SLE pathogenesis.

    Weaknesses:

    Although the manuscript is well-organized and clearly stated, there are some points below that should be considered:

    * In this study, the authors used forward genetic analyses to identify novel gene mutations that may cause SLE, combined with GWAS studies of SLE. To further explore the importance of these variants, haplotype analysis of two candidate genes could be performed, to observe the evolution and selection relationship of candidate genes in the population (UK 1000 biobank, for example).

    * Although the authors focused on SLE and macrophage efferocytosis in their studies, direct evidence of how macrophage efferocytosis significantly affects SLE is lacking. This point should at least be explicitly introduced and discussed by citing appropriate literature.

    * It is still not clear how the target molecules identified in this paper may influence macrophage efferocytosis. More direct evidence should be established.

    * For some transcriptional repressors mentioned in their studies, the authors should check whether there is clear experimental evidence. If not, it is recommended to supplement the experimental verifications for clarity.

    * In Figures 4C and 4D, it is seen that the usage of inhibitors causes cytoskeletal changes, however this reviewer would not have expected such large change. Did the authors check whether the cells die after heavy treatment by the inhibitors?