Project description:A novel heterozygous germline variant, c.547G>A (p.Gly183Ser), in the paired box protein encoding gene, PAX5, was found to segregate with disease in two unrelated kindreds with autosomal dominant pre-B cell acute lymphoblastic leukemia (ALL). Leukemic cells from both families exhibited 9p deletion, with loss-of-heterozygosity and retention of the mutant PAX5 allele at 9p13. Two additional sporadic ALL cases with 9p loss demonstrated PAX5 Gly183 substitution in the leukemic cells. Functional and gene expression analysis of the PAX5 germline variants demonstrated reduced transcriptional activity. These data extend the role of PAX5 alterations in the pathogenesis of pre-B ALL, and implicate PAX5 in a novel syndrome of germline susceptibility to pre-B cell neoplasia. We analyzed 40 samples comprising sevenfold replicates of transductions with empty vector, wild type PAX5 and 4 mutant PAX5 constructs
Project description:A novel heterozygous germline variant, c.547G>A (p.Gly183Ser), in the paired box protein encoding gene, PAX5, was found to segregate with disease in two unrelated kindreds with autosomal dominant pre-B cell acute lymphoblastic leukemia (ALL). Leukemic cells from both families exhibited 9p deletion, with loss-of-heterozygosity and retention of the mutant PAX5 allele at 9p13. Two additional sporadic ALL cases with 9p loss demonstrated PAX5 Gly183 substitution in the leukemic cells. Functional and gene expression analysis of the PAX5 germline variants demonstrated reduced transcriptional activity. These data extend the role of PAX5 alterations in the pathogenesis of pre-B ALL, and implicate PAX5 in a novel syndrome of germline susceptibility to pre-B cell neoplasia.
Project description:A novel heterozygous germline variant, c.547G>A (p.Gly183Ser), in the paired box protein encoding gene, PAX5, was found to segregate with disease in two unrelated kindreds with autosomal dominant pre-B cell acute lymphoblastic leukemia (ALL). Leukemic cells from both families exhibited 9p deletion, with loss-of-heterozygosity and retention of the mutant PAX5 allele at 9p13. Two additional sporadic ALL cases with 9p loss demonstrated PAX5 Gly183 substitution in the leukemic cells. Functional and gene expression analysis of the PAX5 germline variants demonstrated reduced transcriptional activity. These data extend the role of PAX5 alterations in the pathogenesis of pre-B ALL, and implicate PAX5 in a novel syndrome of germline susceptibility to pre-B cell neoplasia.
Project description:A novel heterozygous germline variant, c.547G>A (p.Gly183Ser), in the paired box protein encoding gene, PAX5, was found to segregate with disease in two unrelated kindreds with autosomal dominant pre-B cell acute lymphoblastic leukemia (ALL). Leukemic cells from both families exhibited 9p deletion, with loss-of-heterozygosity and retention of the mutant PAX5 allele at 9p13. Two additional sporadic ALL cases with 9p loss demonstrated PAX5 Gly183 substitution in the leukemic cells. Functional and gene expression analysis of the PAX5 germline variants demonstrated reduced transcriptional activity. These data extend the role of PAX5 alterations in the pathogenesis of pre-B ALL, and implicate PAX5 in a novel syndrome of germline susceptibility to pre-B cell neoplasia. We analyzed 10 samples of J558 murine myeloma cells infected with MSCV-Puro-IRES-GFP (PIG) empty vector (EV; three independent replicates), MSCV-PIG Pax5 WT (WT; three independent replicates), and MSCV-PIG Pax5 G183S (Mut; four independent replicates). Cells were selected with puromycin after infection for 5-7 days, subsequently cells were sorted for GFP and IgM expression by FACS.
Project description:A novel heterozygous germline variant, c.547G>A (p.Gly183Ser), in the paired box protein encoding gene, PAX5, was found to segregate with disease in two unrelated kindreds with autosomal dominant pre-B cell acute lymphoblastic leukemia (ALL). Leukemic cells from both families exhibited 9p deletion, with loss-of-heterozygosity and retention of the mutant PAX5 allele at 9p13 . Two additional sporadic ALL cases with 9p loss demonstrated PAX5 Gly183 substitution in the leukemic cells. Functional analysis of the PAX5 germline variants demonstrated reduced transcriptional activity, as well as decreased interaction with Groucho-4. These data extend the role of PAX5 alterations in the pathogenesis of pre-B ALL, and implicate PAX5 in a novel syndrome of germline susceptibility to pre-B cell neoplasia.
Project description:We used microarrays to analyze gene expression changes in leukemic bone marrow cells from Pax5+/- and WT mice, comparing them with preleukemic bone marrow precursor B cells from both genotypes. All mice were exposed to a single low-dose irradiation (2 Gy). PAX5 is a master regulator of B-cell development, and germline mutations in PAX5 predispose individuals to B-cell acute lymphoblastic leukemia (B-ALL). While PAX5 alterations are a hallmark of B-ALL, the mechanisms linking inherited susceptibility to leukemic transformation remain poorly understood. Here, we provide in vivo genetic evidence demonstrating that reduced Pax5 dosage increases sensitivity to DNA damage, acting as a key factor in B-ALL initiation. Using a mouse model of Pax5 heterozygosity, we show that exposure to a single low-dose irradiation (2 Gy) significantly accelerates leukemia onset, establishing a direct link between genetic predisposition and environmental stress. Notably, the resulting murine B-ALLs closely resemble the human disease, exhibiting complete Pax5 loss, CD19 downregulation, and a high incidence of DNA double-strand breaks. Mechanistically, we identify Pax5 as a regulator of p53-mediated DNA damage responses in preleukemic B cells, highlighting its role beyond lineage specification. These findings provide a mechanistic framework for the interplay between PAX5 deficiency, genomic instability, and environmental factors in early B-ALL development, uncovering new potential vulnerabilities for therapeutic intervention.
Project description:PAX5, one of nine members of the mammalian paired box (PAX) family of transcription factors, plays an important role in B cell development. Approximately one-third of individuals with pre-B acute lymphoblastic leukemia (ALL) acquire heterozygous inactivating mutations of PAX5 in malignant cells, and heterozygous germline loss-offunction PAX5 mutations cause autosomal dominant predisposition to ALL. At least in mice, Pax5 is required for pre-B cell maturation, and leukemic remission occurs when Pax5 expression is restored in a Pax5-deficient mouse model of ALL. Together, these observations indicate that PAX5 deficiency reversibly drives leukemogenesis. PAX5 and its two most closely related paralogs, PAX2 and PAX8, which are not mutated in ALL, exhibit overlapping expression and function redundantly during embryonic development. However, PAX5 alone is expressed in lymphocytes, while PAX2 and PAX8 are predominantly specific to kidney and thyroid, respectively. We show that forced expression of PAX2 or PAX8 complements PAX5 loss-of-function mutation in ALL cells as determined by modulation of PAX5 target genes, restoration of immunophenotypic and morphological differentiation, and, ultimately, reduction of replicative potential. Activation of PAX5 paralogs, PAX2 or PAX8, ordinarily silenced in lymphocytes, may therefore represent a novel approach for treating PAX5-deficient ALL. In pursuit of this strategy, we took advantage of the fact that, in kidney, PAX2 is upregulated by extracellular hyperosmolarity. We found that hyperosmolarity, at potentially clinically achievable levels, transcriptionally activates endogenous PAX2 in ALL cells via a mechanism dependent on NFAT5, a transcription factor coordinating response to hyperosmolarity. We also found that hyperosmolarity upregulates residual wild type PAX5 expression in ALL cells and modulates gene expression, including in PAX5-mutant primary ALL cells. These findings specifically demonstrate that osmosensing pathways may represent a new therapeutic target for ALL and more broadly point toward the possibility of using gene paralogs to rescue mutations driving cancer and other diseases.
Project description:Interleukin-7 receptor α (encoded by IL7R) is essential for lymphoid development. Whether acute lymphoblastic leukemia (ALL)-related IL7R gain-of-function mutations can trigger leukemogenesis remains unclear. Here, we demonstrate that lymphoid-restricted mutant IL7R, expressed at physiological levels in conditional knock-in mice, establishes a pre-leukemia stage in which B-cell precursors display self-renewal ability, initiating precursor B-ALL that resembles PAX5 P80R or Ph-like human leukemia. Full transformation associates with transcriptional upregulation of oncogenes such as Myc or Bcl2, downregulation of tumor suppressors such as Ikzf1 or Arid2, and major IL-7R signaling upregulation (involving both JAK/STAT5 and PI3K/mTOR), required for leukemia cell viability. Accordingly, maximal signaling drives full penetrance and early leukemia onset in homozygous IL7R mutant animals. Notably, we identify 2 transcriptional subgroups in mouse and human Ph-like ALL, and show that dactolisib and sphingosine-kinase inhibitors are novel treatment avenues for IL-7R-related cases. Our model, a unique resource to explore the pathophysiology and therapeutic vulnerabilities of B-ALL, demonstrates that IL7R can initiate this malignancy.