Carla Sebastiani

A new monoclonal antibody (MUM1p) was used to study the cell/tissue expression of human MUM1/IRF4 protein, the product of the homologous gene involved in the myeloma-associated t(6;14) (p25;q32). MUM1 was expressed in the nuclei and cytoplasm of plasma cells and a small percentage of germinal center (GC) B cells mainly located in the "light zone." Its morphologic spectrum ranged from that of centrocyte to that of a plasmablast/plasma cell, and it displayed a phenotype (MUM1(+)/Bcl-6(-)/Ki67(-)) different from that of most GC B cells (MUM1(-)/Bcl-6(+)/Ki67(+)) and mantle B cells (MUM1(-)/Bcl-6(-)/Ki67(-)). Polymerase chain reaction (PCR) analysis of single MUM1(+ )cells isolated from GCs showed that they contained rearranged Ig heavy chain genes with a varying number of V(H) somatic mutations. These findings suggest that these cells may represent surviving centrocytes and their progeny committed to exit GC and to differentiate into plasma cells. MUM1 was strongly expressed in lymphoplasmacytoid lymphoma, multiple myeloma, and approximately 75% of diffuse large B-cell lymphomas (DLCL-B). Unlike normal GC B cells, in which the expression of MUM1 and Bcl-6 were mutually exclusive, tumor cells in approximately 50% of MUM1(+) DLCL-B coexpressed MUM1 and Bcl-6, suggesting that expression of these proteins may be deregulated. In keeping with their proposed origin from GC B cells, Hodgkin and Reed-Sternberg cells of Hodgkin's disease consistently expressed MUM1. MUM1 was detected in normal and neoplastic activated T cells, and its expression usually paralleled that of CD30. These results suggest that MUM1 is involved in the late stages of B-cell differentiation and in T-cell activation and is deregulated in DLCL-B. (Blood. 2000;95:2084-2092)

Acute myelogenous leukemias (AMLs) are genetically heterogeneous and characterized by chromosomal rearrangements that produce fusion proteins with aberrant transcriptional regulatory activities. Expression of AML fusion proteins in transgenic mice increases the risk of myeloid leukemias, suggesting that they induce a preleukemic state. The underlying molecular and biological mechanisms are, however, unknown. To address this issue, we performed a systematic analysis of fusion protein transcriptional targets. We expressed AML1/ETO, PML/RAR, and PLZF/RAR in U937 hemopoietic precursor cells and measured global gene expression using oligonucleotide chips. We identified 1,555 genes regulated concordantly by at least two fusion proteins that were further validated in patient samples and finally classified according to available functional information. Strikingly, we found that AML fusion proteins induce genes involved in the maintenance of the stem cell phenotype and repress DNA repair genes, mainly of the base excision repair pathway. Functional studies confirmed that ectopic expression of fusion proteins constitutively activates pathways leading to increased stem cell renewal (e.g., the Jagged1/Notch pathway) and provokes accumulation of DNA damage. We propose that expansion of the stem cell compartment and induction of a mutator phenotype are relevant features underlying the leukemic potential of AML-associated fusion proteins.

The majority of proteins in cow’s milk are caseins, which occur in four groups (α-s1, α-s2, β, and k) encoded by different genes (CSN1S1, CSN1S2, CSN2, and CSN3, respectively). In this study, we focused on the β-casein allele variants A1 and A2 due to their influence on milk’s technological characteristics and human health. Digestion of the β-casein variant A1 leads to the formation of β-casomorphin 7 (BCM-7), a bioactive peptide that has been suggested to be a possible cause of various human diseases and associated with low milk digestibility. The potential negative role of the β-casein variant A1 in human health has stimulated the planning of cattle breeding programs based on genetic selection to increase the frequency of the A2 variant, which is associated with increased milk digestibility. The aim of this work was to evaluate the frequencies of the different β-casein variants in Italian Holstein Friesian dairy cows from cattle farms located in central Italy to select a population of A2 homozygous animals. β-casein genotypes were identified by evaluating the presence of single nucleotide polymorphisms (SNPs) of the CSN2 gene using PCR and sequencing analysis. The frequency of the desirable β-casein variant A2 in the studied bovine population was 0.61. The frequency of the undesirable A1 variant in the studied bovine population was 0.30. The frequency of the A2 allele was higher than expected for the breed; therefore, genetic selection for the A2 variant in these animals could be achieved in a fairly short time using A2 homozygous bulls.