FHL2 interacts with CALM and is highly expressed in acute erythroid leukemia.

The t(10;11)(p13;q14) translocation results in the fusion of the CALM (clathrin assembly lymphoid myeloid leukemia protein) and AF10 genes. This translocation is observed in acute myeloblastic leukemia (AML M6), acute lymphoblastic leukemia (ALL) and malignant lymphoma. Using a yeast two-hybrid screen, the four and a half LIM domain protein 2 (FHL2) was identified as a CALM interacting protein. Recently, high expression of FHL2 in breast, gastric, colon, lung as well as in prostate cancer was shown to be associated with an adverse prognosis. The interaction between CALM and FHL2 was confirmed by glutathione S-transferase-pulldown assay and co-immunoprecipitation experiments. The FHL2 interaction domain of CALM was mapped to amino acids 294-335 of CALM. The transcriptional activation capacity of FHL2 was reduced by CALM, but not by CALM/AF10, which suggests that regulation of FHL2 by CALM might be disturbed in CALM/AF10-positive leukemia. Extremely high expression of FHL2 was seen in acute erythroid leukemia (AML M6). FHL2 was also highly expressed in chronic myeloid leukemia and in AML with complex aberrant karyotype. These results suggest that FHL2 may play an important role in leukemogenesis, especially in the case of AML M6.

Cloning and expression analysis of SALL4, the murine homologue of the gene mutated in Okihiro syndrome.

SALL4 is one out of four human homologues of the DROSOPHILA region-specific homeotic gene SPALT(SAL). Heterozygous mutations of SALL4 on chromosome 20q13.13--> q13.2 cause the autosomal dominant Okihiro syndrome which is characterized by radial limb defects, Duane anomaly and hearing loss. We have partially cloned the murine homologue of this gene, named SALL4, and completed the coding sequence by comparison to available EST and genomic sequences in the GenBank database. This comparison also revealed the chromosomal location of SALL4 on mouse chromosome 2H3 and suggested that a predicted testis expressed gene TEX20 at the very same locus is most likely not a gene on its own but part of the SALL4 3' UTR. We analyzed the expression of SALL4 during early embryogenesis by whole mount in situ hybridization and in the adult mouse by Northern blotting. In adult tissues, SALL4 expression is only found in testis and ovary. During embryonic development, SALL4 expression is widespread in early embryos and becomes gradually confined to the head region and the primitive streak. Prominent expression in the developing midbrain, branchial arches and the limbs suggests an important function of SALL4 during development of these structures as expected from the observation in Okihiro syndrome patients.