👤 Annabelle Monnier

While TPM2 mutations identified so far in muscular diseases were all associated with a dominant inheritance pattern, we report the identification of a homozygous null allele mutation in the TPM2 gene in a patient who presented with a recessive form of nemaline myopathy associated with a non-lethal multiple pterygium syndrome (Escobar-MPS MIM# 265000). The TPM2 mutation led to a complete absence of the skeletal muscle isoform of beta-tropomyosin not compensated by expression of other beta-tropomyosin isoforms. Escobar syndrome has been recently described as a prenatal form of myasthenia associated with recessive mutations in genes of the neuromuscular junction (CHRNG, CHRNA1, CHRND, RAPSN). This observation expands the cause of Escobar variant-MPS to a component of the contractile apparatus. This first report of the clinical expression of the complete absence of TPM2 in human indicated that TPM2 expression at the early period of prenatal life plays a major role for normal fetal movements. Show less

The t(12;21)(p13;q22) translocation is found in 20 to 25% of cases of childhood B-lineage acute lymphoblastic leukemia (B-ALL). This rearrangement results in the fusion of ETV6 (TEL) and RUNX1 (AML1) genes and defines a relatively uniform category, although only some patients suffer very late relapse. TEL/AML1-positive patients are thus an interesting subgroup to study, and such studies should elucidate the biological processes underlying TEL/AML1 pathogenesis. We report an analysis of gene expression in 60 children with B-lineage ALL using Agilent whole genome oligo-chips (44K-G4112A) and/or real time RT-PCR. We compared the leukemia cell gene expression profiles of 16 TEL/AML1-positive ALL patients to those of 44 TEL/AML1-negative patients, whose blast cells did not contain any additional recurrent translocation. Microarray analyses of 26 samples allowed the identification of genes differentially expressed between the TEL/AML1-positive and negative ALL groups. Gene enrichment analysis defined five enriched GO categories: cell differentiation, cell proliferation, apoptosis, cell motility and response to wounding, associated with 14 genes -RUNX1, TCFL5, TNFRSF7, CBFA2T3, CD9, SCARB1, TP53INP1, ACVR1C, PIK3C3, EGFL7, SEMA6A, CTGF, LSP1, TFPI - highlighting the biology of the TEL/AML1 sub-group. These results were first confirmed by the analysis of an additional microarray data-set (7 patient samples) and second by real-time RT-PCR quantification and clustering using an independent set (27 patient samples). Over-expression of RUNX1 (AML1) was further investigated and in one third of the patients correlated with cytogenetic findings. Gene expression analyses of leukemia cells from 60 children with TEL/AML1-positive and -negative B-lineage ALL led to the identification of five biological processes, associated with 14 validated genes characterizing and highlighting the biology of the TEL/AML1-positive ALL sub-group. Show less