A p53-dependent mechanism underlies macrocytic anemia in a mouse model of human 5q- syndrome.

The identification of the genes associated with chromosomal translocation breakpoints has fundamentally changed understanding of the molecular basis of hematological malignancies. By contrast, the study of chromosomal deletions has been hampered by the large number of genes deleted and the complexity of their analysis. We report the generation of a mouse model for human 5q- syndrome using large-scale chromosomal engineering. Haploinsufficiency of the Cd74-Nid67 interval (containing Rps14, encoding the ribosomal protein S14) caused macrocytic anemia, prominent erythroid dysplasia and monolobulated megakaryocytes in the bone marrow. These effects were associated with defective bone marrow progenitor development, the appearance of bone marrow cells expressing high amounts of the tumor suppressor p53 and increased bone marrow cell apoptosis. Notably, intercrossing with p53-deficient mice completely rescued the progenitor cell defect, restoring common myeloid progenitor and megakaryocytic-erythroid progenitor, granulocyte-monocyte progenitor and hematopoietic stem cell bone marrow populations. This mouse model suggests that a p53-dependent mechanism underlies the pathophysiology of the 5q- syndrome

Characterization of a Monoclonal Antibody Directed against Mytilus spp Larvae Reveals an Antigen Involved in Shell Biomineralization.

The M22.8 monoclonal antibody (mAb) developed against an antigen expressed at the mussel larval and postlarval stages of Mytilus galloprovincialis was studied on adult samples. Antigenic characterization by Western blot showed that the antigen MSP22.8 has a restricted distribution that includes mantle edge tissue, extrapallial fluid, extrapallial fluid hemocytes, and the shell organic matrix of adult samples. Other tissues such as central mantle, gonadal tissue, digestive gland, labial palps, foot, and byssal retractor muscle did not express the antigen. Immunohistochemistry assays identified MSP22.8 in cells located in the outer fold epithelium of the mantle edge up to the pallial line. Flow cytometry analysis showed that hemocytes from the extrapallial fluid also contain the antigen intracellularly. Furthermore, hemocytes from hemolymph have the ability to internalize the antigen when exposed to a cell-free extrapallial fluid solution. Our findings indicate that hemocytes could play an important role in the biomineralization process and, as a consequence, they have been included in a model of shell formation. This is the first report concerning a protein secreted by the mantle edge into the extrapallial space and how it becomes part of the shell matrix framework in M. galloprovincialis mussels

Histology of the mantle edge in adult <i>M</i>. <i>galloprovincialis</i>.

<p>Hematoxilin-eosin stain, 4× microphotographs. (o.f): outer fold; (m.f): middle fold; (p.g): periostracal groove; (p): periostracum.</p

Immunostaining of the mantle edge in adult <i>M</i>. <i>Galloprovincialis</i> with M22.8 mAb and revealed with DAB.

<p>(o.f): outer fold; (m.f): middle fold; (p.g): periostracal groove; (i.f): inner fold.</p

Model of the cell-mediated shell formation in <i>M</i>.<i>galloprovincialis</i>.

<p>The size of the extrapallial cavity is enlarged for the sake of clarity.</p

Immunostaining of the mantle edge of adult M. galloprovincialis with M22.8 mAb.

<p>Microphotographs were taken at 4× (a, b, c) and 10× (d,e,f). (o.f): outer fold; (m.f): middle fold; (p.g): periostracal groove; (a,d) negative control; (b,e): immunostaining revealed with VectorVip; (c,f) immunostaining revealed with DAB.</p

Flow cytometry analysis of permeabilized hemocytes.

<p>(a) EP hemocytes used as positive control; (b) hemolymph hemocytes exposed to sea water; (c) hemolymph hemocytes exposed to EPF cell-free solution. Cells were incubated with the M22.8 mAb followed by FITC-labelled secondary antibodies. (MFI): median fluorescence intensity; (HL): hemolymph.</p

Western blot assay on M. <i>galloprovincialis</i> shell organic matrix.

<p>(1) EPF as positive control; (2) molecular weight markers (kDa); (3,4,5,6) <i>Mytilus galloprovincialis</i> shell organic matrix from different mussels.</p

Western blot assays on hemocytes from adult <i>M</i>. <i>galloprovincialis</i>.

<p>(1) molecular weight markers (kDa); (2, 3, 4) EP hemocytes; (5) hemolymph hemocytes; (6) empty well.</p