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Association of aberrant ASNS imprinting with asparaginase sensitivity and chromosomal abnormality in childhood BCP-ALL.

ABSTRACT: Karyotype is an important prognostic factor in childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL), but the underlying pharmacogenomics remain unknown. Asparaginase is an integral component in current chemotherapy for childhood BCP-ALL. Asparaginase therapy depletes serum asparagine. Normal hematopoietic cells can produce asparagine by asparagine synthetase (ASNS) activity, but ALL cells are unable to synthesize adequate amounts of asparagine. The ASNS gene has a typical CpG island in its promoter. Thus, methylation of the ASNS CpG island could be one of the epigenetic mechanisms for ASNS gene silencing in BCP-ALL. To gain deep insights into the pharmacogenomics of asparaginase therapy, we investigated the association of ASNS methylation status with asparaginase sensitivity. The ASNS CpG island is largely unmethylated in normal hematopoietic cells, but it is allele-specifically methylated in BCP-ALL cells. The ASNS gene is located at 7q21, an evolutionally conserved imprinted gene cluster. ASNS methylation in childhood BCP-ALL is associated with an aberrant methylation of the imprinted gene cluster at 7q21. Aberrant methylation of mouse Asns and a syntenic imprinted gene cluster is also confirmed in leukemic spleen samples from ETV6-RUNX1 knockin mice. In 3 childhood BCP-ALL cohorts, ASNS is highly methylated in BCP-ALL patients with favorable karyotypes but is mostly unmethylated in BCP-ALL patients with poor prognostic karyotypes. Higher ASNS methylation is associated with higher L-asparaginase sensitivity in BCP-ALL through lower ASNS gene and protein expression levels. These observations demonstrate that silencing of the ASNS gene as a result of aberrant imprinting is a pharmacogenetic mechanism for the leukemia-specific activity of asparaginase therapy in BCP-ALL.

SUBMITTER: Watanabe A

PROVIDER: S-EPMC7702480 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The Amyotrophic Lateral Sclerosis/Parkinsonism-Dementia Complex (Kii ALS/PDC), a rare and complex neurological disorder, is predominantly observed in the Western Pacific islands, including regions of Japan, Guam, and Papua. This enigmatic condition continues to capture medical attention due to patients displaying symptoms that parallel those seen in either classical amyotrophic lateral sclerosis (ALS) or Parkinson's Disease (PD). Distinctly, post-mortem examinations of the brains of affected individuals have shown concurrent hallmarks: the presence of α-synuclein aggregates, which are a signature of PD, and TDP-43, associated with classical ALS. These observations are further complicated by the detection of phosphorylated tau, accentuating the multifaceted proteinopathic nature of Kii ALS/PDC. The etiological foundations of this disease remain undetermined, and genetic investigations have yet to provide conclusive answers. However, emerging evidence has cast a spotlight on astrocytes, cells pivotal for maintaining brain health. These astrocytes are likely to play a significant role in the pathogenesis of Kii ALS/PDC. Leveraging advanced iPSC technology, our team cultivated multiple astrocyte lines to probe the disease further. CHCHD2 emerged as asignificantly dysregulated gene when disease astrocytes were compared to healthy controls. Our analyses also unveiled imbalances in specific pathways: those associated with astrocytic cilium dysfunction, known to have ties with neurodegeneration, and those related to major neurological disorders, including classical ALS and PD. Further in-depth examinations revealed abnormalities in the mitochondrial morphology and metabolic processes of the affected astrocytes. A particularly striking observation was the reduced expression of CHCHD2 in a patient’s spinal cord. In sum, our findings suggest a potential compromise in the support Kii ALS/PDC astrocytes provide to neurons, emphasizing the need to explore the role of CHCHD2 in maintaining mitochondrial health and its implications for the disease.

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Association of aberrant ASNS imprinting with asparaginase sensitivity and chromosomal abnormality in childhood BCP-ALL.

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