Integrins are the major adhesion receptors of leukocytes and platelets. β 1 and β 2 integrin function on leukocytes is crucial for a successful immune response and the platelet integrin α IIb β 3 initiates the process of blood clotting through binding fibrinogen1-3. Integrins on circulating cells bind poorly to their ligands but become active after 'inside-out' signaling through other membrane receptors4,5. Subjects with leukocyte adhesion deficiency-1 (LAD-I) do not express β 2 integrins because of mutations in the gene specifying the β 2 subunit, and they suffer recurrent bacterial infections6,7. Mutations affecting α IIb β 3 integrin cause the bleeding disorder termed Glanzmann's thrombasthenia3. Subjects with LAD-III show symptoms of both LAD-I and Glanzmann's thrombasthenia. Their hematopoietically-derived cells express β 1 , β 2 and β 3 integrins, but defective inside-out signaling causes immune deficiency and bleeding problems8. The LAD-III lesion has been attributed to a C→A mutation in the gene encoding calcium and diacylglycerol guanine nucleotide exchange factor (CALDAGGEF1; official symbol RASGRP2) specifying the CALDAG-GEF1 protein9, but we show that this change is not responsible for the LAD-III disorder. Instead, we identify mutations in the KINDLIN3 (official symbol FERMT3) gene specifying the KINDLIN-3 protein as the cause of LAD-III in Maltese and Turkish subjects. Two independent mutations result in decreased KINDLIN3 messenger RNA levels and loss of protein expression. Notably, transfection of the subjects' lymphocytes with KINDLIN3 complementary DNA but not CALDAGGEF1 cDNA reverses the LAD-III defect, restoring integrin-mediated adhesion and migration.

The serine-threonine kinase LKB1 regulates cell polarity from Caenorhabditis elegans to man. Loss of lkb1 leads to a cancer predisposition, known as Peutz-Jeghers Syndrome. Biochemical analysis indicates that LKB1 can phosphorylate and activate a family of AMPK-like kinases, however, the precise contribution of these kinases to the establishment and maintenance of cell polarity is still unclear. Recent studies propose that LKB1 acts primarily through the AMP kinase to establish and/or maintain cell polarity. To determine whether this simple model of how LKB1 regulates cell polarity has relevance to complex tissues, we examined lkb1 mutants in the Drosophila eye. We show that adherens junctions expand and apical, junctional, and basolateral domains mix in lkb1 mutants. Surprisingly, we find LKB1 does not act primarily through AMPK to regulate cell polarity in the retina. Unlike lkb1 mutants, ampk retinas do not show elongated rhabdomeres or expansion of apical and junctional markers into the basolateral domain. In addition, nutrient deprivation does not reveal a more dramatic polarity phenotype in lkb1 photoreceptors. These data suggest that AMPK is not the primary target of LKB1 during eye development. Instead, we find that a number of other AMPK-like kinase, such as SIK, NUAK, Par-1, KP78a, and KP78b show phenotypes similar to weak lkb1 loss of function in the eye. These data suggest that in complex tissues, LKB1 acts on an array of targets to regulate cell polarity.AMPK ͉ SIK ͉ NUAK ͉ Par-1 ͉ KP78

Solid pseudopapillary tumor (SPT) of the pancreas is an uncommon neoplasm of uncertain lineage. They have been shown to express nuclear beta-catenin believed to be due to mutations of the beta-catenin gene. The aim of this study was to investigate the status of the E-cadherin/catenin complex in SPTs. We studied the expression of 4 principal members of the E-cadherin/catenin complex using immunohistochemistry and the E-cadherin gene status by screening all exons of the gene for mutations, in 6 cases of SPT. In addition to the nuclear localization of beta-catenin, we found nuclear localization of E-cadherin in all tumors with complete absence of membranous and cytoplasmic localization. Nuclear localization of E-cadherin was independent of beta-catenin. No mutations were identified in the E-cadherin gene in any of the tumors. Ten cases of pancreatic adenocarcinomas and 15 neuroendocrine tumors were studied as well for comparison. The reported changes in the expression of the principal members of the E-cadherin/catenin complex were unique to SPTs. Our study shows abnormalities in the expression of 4 principal members of the E-cadherin/catenin complex in SPTs, which may help to explain the discohesive nature of the cells and the cystic changes in these tumors, and provide additional diagnostic features.

The E-cadherin/catenin complex is a prime mediator of cell-cell adhesion. APC mutations can result in loss of beta-catenin downregulation and an accumulation of beta-catenin in the cell. Beta-CATENIN mutations can have a similar effect. The aim of this study was to investigate the effect of beta-CATENIN and APC mutations on the expression and assembly of the E-cadherin/catenin complex. Five colorectal carcinoma cell lines with different APC and beta-CATENIN gene status were selected and mutations were confirmed. The expression of members of the E-cadherin/catenin complex was studied by immunohistochemistry and Western blotting. Complex assembly was investigated by immunoprecipitation. It is shown that E-cadherin and catenins are expressed in colorectal carcinoma cell lines with the predominant complex assembly being E-cadherin/beta-catenin/alpha-catenin. The subcellular distribution of the proteins is influenced by cell-cell contact, resulting in membranous localization. The expression and assembly of the E-cadherin/catenin complex does not appear to be affected by the presence of APC and or beta-CATENIN mutations.

Previously we have localized to chromosome 3q21-q24, a predisposition locus for colorectal cancer (CRC), through a genome-wide linkage screen (GWLS) of 69 families without familial adenomatous polyposis or hereditary non-polyposis CRC. To further investigate Mendelian susceptibility to CRC, we extended our screen to include a further GWLS of an additional 34 CRC families. We also searched for a disease gene at 3q21-q24 by linkage disequilibrium mapping in 620 familial CRC cases and 960 controls by genotyping 1676 tagging SNPs and sequencing 30 candidate genes from the region. Linkage analysis was conducted using the Affymetrix 10K SNP array. Data from both GWLSs were pooled and multipoint linkage statistics computed. The maximum NPL score (3.01; P ¼ 0.0013) across all families was at 3q22, maximal evidence for linkage coming from families segregating rectal CRC. The same genomic position also yielded the highest multipoint heterogeneity LOD (HLOD) score under a dominant model (HLOD ¼ 2.79; P ¼ 0.00034), with an estimated 43% of families linked. In the case-control analysis, the strongest association was obtained at rs698675 (P ¼ 0.0029), but this was not significant after adjusting for multiple testing. Analysis of candidate gene mapping to the region of maximal linkage on 3q22 failed to identify a causal mutation. There was no evidence for linkage to the previously reported 9q CRC locus (NPL ¼ 0. 1 It is therefore likely that a significant proportion of inherited predisposition to CRC is mediated through susceptibility to CRAs. These observations have provided a strong rationale for searching of novel predisposition genes through genome-wide linkage screens (GWLSs) of hereditary non-FAP/HNPCC CRC families (hereditary nonsyndromic colorectal cancer -HNSCRC). Using a high-density SNP array, we have previously performed a GWLS of 69 HNSCRC families in which involvement of known predisposition genes had been excluded and a novel CRC susceptibility locus at 3q21 -q24 was identified. 5 Other workers have proposed additional loci for CRC susceptibility genes on the basis of linkage, most notably on 9q22.2 -31.2. 6,7 To further examine the impact of unknown moderate/ high-penetrance genes on CRC risk, we conducted a further GWLS on an additional 34 HNSCRC families using the same analytical platform employed in our first analysis. We then pooled data from scans. In an effort to predict the most likely location of the putative CRC gene on 3q21 -q24, we undertook linkage disequilibrium (LD) mapping at 1676 tagging SNPs in 620 HNSCRC cases and 961 controls. In addition, we have sought to identify disease-causing variants by direct mutational analysis of candidate genes localizing to the region of maximal linkage on 3q22. Materials and methods Ascertainment and collection of families and casesFor clarity, we refer to our previously reported GWLS of 69 pedigrees as phase 1 8 and the current analysis of 34 pedigrees as phase 2. As before, familial CRC cases were ascertained through the COloRectal tumour Gene Identification (C...

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These results provide important information for healthcare commissioners faced with managing demand for molecular testing of cancers.