Chou SR, Bailey AC, Baysac K, Oler AJ, Milner JD, Ombrello MJ. Splice site and
de novo mutations can cause mixed dominant negative/gain of function
PLCG2-associated immune dysregulation with cold urticaria (CU-PLAID).
medRxiv 2024:2024.03.16.24304180. [PMID:
38562814 PMCID:
PMC10984065 DOI:
10.1101/2024.03.16.24304180]
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Abstract
Background
Phospholipase Cγ2 (PLCγ2) is an important signaling molecule that receives and transmits signals from various cell surface receptors in most hematopoietic lineages. Variants of PLCG2 cause PLCγ2-associated immune dysregulation (PLAID), a family of conditions that are classified by mutational effect. PLAID with cold urticaria (CU-PLAID) is caused by in-frame deletions of PLCG2 that are dominant negative at physiologic temperatures but become spontaneously active at sub-physiologic temperatures.
Objective
To identify genetic lesions that cause PLAID by combining RNA sequencing of full-length PLCG2 with whole genome sequencing.
Methods
We studied nine probands with antibody deficiency and a positive evaporative cooling test, together with two known CU-PLAID patients and three healthy subjects. Illumina sequencing was performed on full-length PLCG2 cDNA synthesized from peripheral blood mononuclear cell RNA and whole genome sequencing was used to identify genetic lesions. Novel alternate transcripts were overexpressed in the Plcg2-deficient DT40 cell overexpression system. ERK phosphorylation was quantified by flow cytometry with and without BCR crosslinking.
Results
Two probands expressed novel alternative transcripts of PLCG2 with in-frame deletions. The first, expressing PLCG2 without exons 18-19, carried a splice site mutation in intron 19. The second, expressing PLCG2 without exons 19-22, carried a 14kb de novo deletion of PLCG2. DT40 cells overexpressing the exon 18-19 or exon 19-22 deletions failed to phosphorylate ERK in response to BCR crosslinking.
Conclusion
In addition to autosomal dominant genomic deletions, de novo deletions and splice site mutations of PLCG2 can also cause CU-PLAID. All of these can be identified by cDNA-based sequencing.
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