Chromosome 19p13.3 deletion in a child with Peutz-Jeghers syndrome, congenital heart defect, high myopia, learning difficulties and dysmorphic features: Clinical and molecular characterization of a new contiguous gene syndrome

The Peutz-Jeghers syndrome (PJS) is an autosomal-dominant hamartomatous polyposis syndrome characterized by mucocutaneous pigmentation, gastrointestinal polyps and the increased risk of multiple cancers. The causative point mutation in the STK11 gene of most patients accounts for about 30% of the cases of partial and complete gene deletion. This is a report on a girl with PJS features, learning difficulties, dysmorphic features and cardiac malformation, bearing a de novo 1.1 Mb deletion at 19p13.3. This deletion encompasses at least 47 genes, including STK11. This is the first report on 19p13.3 deletion associated with a PJS phenotype, as well as other atypical manifestations, thereby implying a new contiguous gene syndrome

A novel mutation in STK11 gene is associated with Peutz-Jeghers Syndrome in Indian patients

BACKGROUND: Peutz-Jeghers syndrome (PJS) is a rare multi-organ cancer syndrome and understanding its genetic basis may help comprehend the molecular mechanism of familial cancer. A number of germ line mutations in the STK11 gene, encoding a serine threonine kinase have been reported in these patients. However, STK11 mutations do not explain all PJS cases. An earlier study reported absence of STK11 mutations in two Indian families and suggested another potential locus on 19q13.4 in one of them. METHODS: We sequenced the promoter and the coding region including the splice-site junctions of the STK11 gene in 16 affected members from ten well-characterized Indian PJS families with a positive family history. RESULTS: We did not observe any of the reported mutations in the STK11 gene in the index patients from these families. We identified a novel pathogenic mutation (c.790_793 delTTTG) in the STK11 gene in one index patient (10%) and three members of his family. The mutation resulted in a frame-shift leading to premature termination of the STK11 protein at 286(th )codon, disruption of kinase domain and complete loss of C-terminal regulatory domain. Based on these results, we could offer predictive genetic testing, prenatal diagnosis and genetic counselling to other members of the family. CONCLUSION: Ours is the first study reporting the presence of STK11 mutation in Indian PJS patients. It also suggests that reported mutations in the STK11 gene are not responsible for the disease and novel mutations also do not account for many Indian PJS patients. Large-scale genomic deletions in the STK11 gene or another locus may be associated with the PJS phenotype in India and are worth future investigation

Repression of osteoblast maturation by ERRalpha accounts for bone loss induced by estrogen deficiency

ERRalpha is an orphan member of the nuclear receptor family, the complete inactivation of which confers resistance to bone loss induced by ageing and estrogen withdrawal to female mice in correlation with increased bone formation in vivo. Furthermore ERRalpha negatively regulates the commitment of mesenchymal cells to the osteoblast lineage ex vivo as well as later steps of osteoblast maturation. We searched to determine whether the activities of ERRalpha on osteoblast maturation are responsible for one or both types of in vivo induced bone loss. To this end we have generated conditional knock out mice in which the receptor is normally present during early osteoblast differentiation but inactivated upon osteoblast maturation. Bone ageing in these animals was similar to that observed for control animals. In contrast conditional ERRalphaKO mice were completely resistant to bone loss induced by ovariectomy. We conclude that the late (maturation), but not early (commitment), negative effects of ERRalpha on the osteoblast lineage contribute to the reduced bone mineral density observed upon estrogen deficiency

The Tripartite Motif Protein MADD-2 Functions with the Receptor UNC-40 (DCC) in Netrin-Mediated Axon Attraction and Branching

Neurons innervate multiple targets by sprouting axon branches from a primary axon shaft. We show here that the ventral guidance factor unc-6 (Netrin), its receptor unc-40 (DCC), and the gene madd-2 stimulate ventral axon branching in C. elegans chemosensory and mechanosensory neurons. madd-2 also promotes attractive axon guidance to UNC-6 and assists unc-6- and unc-40-dependent ventral recruitment of the actin regulator MIG-10 in nascent axons. MADD-2 is a tripartite motif protein related to MID-1, the causative gene for the human developmental disorder Opitz syndrome. MADD-2 and UNC-40 proteins preferentially localize to a ventral axon branch that requires their function; genetic results indicate that MADD-2 potentiates UNC-40 activity. Our results identify MADD-2 as an UNC-40 cofactor in axon attraction and branching, paralleling the role of UNC-5 in repulsion, and provide evidence that targeting of a guidance factor to specific axonal branches can confer differential responsiveness to guidance cues.National Institutes of Health (U.S.) (Grant number GM0680678

Loss of Expression and Promoter Methylation of SLIT2 Are Associated with Sessile Serrated Adenoma Formation.

Serrated adenomas form a distinct subtype of colorectal pre-malignant lesions that may progress to malignancy along a different molecular pathway than the conventional adenoma-carcinoma pathway. Previous studies have hypothesised that BRAF mutation and promoter hypermethylation plays a role, but the evidence for this is not robust. We aimed to carry out a whole-genome loss of heterozygosity analysis, followed by targeted promoter methylation and expression analysis to identify potential pathways in serrated adenomas. An initial panel of 9 sessile serrated adenomas (SSA) and one TSA were analysed using Illumina Goldengate HumanLinkage panel arrays to ascertain regions of loss of heterozygosity. This was verified via molecular inversion probe analysis and microsatellite analysis of a further 32 samples. Methylation analysis of genes of interest was carried out using methylation specific PCR (verified by pyrosequencing) and immunohistochemistry used to correlate loss of expression of genes of interest. All experiments used adenoma samples and normal tissue samples as control. SSA samples were found on whole-genome analysis to have consistent loss of heterozygosity at 4p15.1–4p15.31, which was not found in the sole TSA, adenomas, or normal tissues. Genes of interest in this region were PDCH7 and SLIT2, and combined MSP/IHC analysis of these genes revealed significant loss of SLIT2 expression associated with promoter methylation of SLIT2. Loss of expression of SLIT2 by promoter hypermethylation and loss of heterozygosity events is significantly associated with serrated adenoma development, and SLIT2 may represent a epimutated tumour suppressor gene according to the Knudson “two hit” hypothesis

Functional analysis of Peutz-Jeghers mutations reveals that the LKB1 C-terminal region exerts a crucial role in regulating both the AMPK pathway and the cell polarity.

Germline mutations of the LKB1 gene are responsible for the cancer-prone Peutz-Jeghers syndrome (PJS). LKB1 encodes a serine-threonine kinase that acts as a regulator of cell cycle, metabolism and cell polarity. The majority of PJS missense mutations abolish LKB1 enzymatic activity and thereby impair all functions assigned to LKB1. Here, we have investigated the functional consequences of recurrent missense mutations identified in PJS and in sporadic tumors which map in the LKB1 C-terminal non-catalytic region. We report that these C-terminal mutations neither disrupt LKB1 kinase activity nor interfere with LKB1-induced growth arrest. However, these naturally occuring mutations lessened LKB1-mediated activation of the AMP-activated protein kinase (AMPK) and impaired downstream signaling. Furthermore, C-terminal mutations compromise LKB1 ability to establish and maintain polarity of both intestinal epithelial cells and migrating astrocytes. Consistent with these findings, mutational analysis reveals that the LKB1 tail exerts an essential function in the control of cell polarity. Overall, our results ascribe a crucial regulatory role to the LKB1 C-terminal region. Our findings further indicate that LKB1 tumor suppressor activity is likely to depend on the regulation of AMPK signaling and cell polarization.