Guven Luleci

Identification of the gene (BBS1) most commonly involved in Bardet-Biedl syndrome, a complex human obesity syndrome.

Bardet-Biedl syndrome (BBS, OMIM 209900) is a genetic disorder with the primary features of obesity, pigmentary retinopathy, polydactyly, renal malformations, mental retardation and hypogenitalism. Individuals with BBS are also at increased risk for diabetes mellitus, hypertension and congenital heart disease. What was once thought to be a homogeneous autosomal recessive disorder is now known to map to at least six loci: 11q13 (BBS1), 16q21 (BBS2), 3p13–p12 (BBS3), 15q22.3–q23 (BBS4), 2q31 (BBS5) and 20p12 (BBS6). There has been considerable interest in identifying the genes that underlie BBS, because some components of the phenotype are common. Cases of BBS mapping ro BBS6 are caused by mutations in MKKS; mutations in this gene also cause McKusick-Kaufman syndrome (hydrometrocolpos, post-axial polydactyly and congenital heart defects). In addition, we recently used positional cloning to identify the genes underlying BBS2 (ref. 16) and BBS4 (ref. 17). The BBS6 protein has similarity to a Thermoplasma acidophilum chaperonin, whereas BBS2 and BBS4 have no significant similarity to chaperonins. It has recently been suggested that three mutated alleles (two at one locus, and a third at a second locus) may be required for manifestation of BBS (triallelic inheritance). Here we report the identification of the gene BBS1 and show that a missense mutation of this gene is a frequent cause of BBS. In addition, we provide data showing that this common mutation is not involved in triallelic inheritance.

Evaluation of Complex Inheritance Involving the Most Common Bardet-Biedl Syndrome Locus (BBS1)

Bardet-Biedl syndrome (BBS) is a genetic disorder with the primary features of obesity, pigmentary retinopathy, polydactyly, renal malformations, mental retardation, and hypogenitalism. Patients with BBS are also at increased risk for diabetes mellitus, hypertension, and congenital heart disease. BBS is known to map to at least six loci: 11q13 (BBS1), 16q21 (BBS2), 3p13-p12 (BBS3), 15q22.3-q23 (BBS4), 2q31 (BBS5), and 20p12 (BBS6). Although these loci were all mapped on the basis of an autosomal recessive mode of inheritance, it has recently been suggested-on the basis of mutation analysis of the identified BBS2, BBS4, and BBS6 genes-that BBS displays a complex mode of inheritance in which, in some families, three mutations at two loci are necessary to manifest the disease phenotype. We recently identified BBS1, the gene most commonly involved in Bardet-Biedl syndrome. The identification of this gene allows for further evaluation of complex inheritance. In the present study we evaluate the involvement of the BBS1 gene in a cohort of 129 probands with BBS and report 10 novel BBS1 mutations. We demonstrate that a common BBS1 missense mutation accounts for approximately 80% of all BBS1 mutations and is found on a similar genetic background across populations. We show that the BBS1 gene is highly conserved between mice and humans. Finally, we demonstrate that BBS1 is inherited in an autosomal recessive manner and is rarely, if ever, involved in complex inheritance.

In vivo and in vitro regulation of Akt activation in human endometrial cells is estrogen dependent

Abstract Estrogen-bound estrogen receptors (ER) α and β classically activate gene expression after binding to the estrogen response element in the promoter regions of target genes. Estrogen also has rapid, nongenomic effects. It activates several membranous or cytoplasmic kinase cascades, including the phosphatidylinositol 3-phosphate (PI3K/Akt) cascade, a signaling pathway that plays a key role in cell survival and apoptosis. Normal human endometrium is exposed to variable levels of steroid hormones throughout the menstrual cycle. We hypothesized that Akt phosphorylation in human endometrium may vary with the menstrual cycle and in early pregnancy and that fluctuations in estrogen level may play a role in Akt activation in endometrial cells. We analyzed Akt phosphorylation using in vivo and in vitro techniques, including Western blot, immunohistochemistry, and immunocytochemistry. Estradiol significantly increased Akt phosphorylation in endometrial cells. Rapid stimulation of Akt activation in cultured stromal cells was observed. Akt phosphorylation by estradiol was inhibited by the PI3K inhibitor, wortmannin, but not by the ER antagonist, ICI 182 780. The maximal effect on Akt activity was observed following 5–15 min of estradiol treatment. Our results suggest that estradiol may directly affect PI3K-related signaling pathway by increasing the phosphorylation of Akt in endometrial cells. Thus, estradiol may exert part of its proliferative and antiapoptotic effects by a nongenomic manner through the Akt signaling pathway.

Rate Limiting Steps of AAV Transduction and Implications for Human Gene Therapy

Despite the fact that adeno-associated virus type 2 (AAV2) is an extremely attractive gene therapy vector, its application has been limited to certain tissues such as muscle and the brain. In an attempt to broaden the array of target organs for this vector, molecular studies on the mechanism(s) of AAV transduction have expanded over the past several years. These studies have led to the development of innovative strategies capable of overcoming intracellular barriers to AAV2 transduction. The basis of these technologic breakthroughs has stemmed from a better understanding of the molecular processes that control AAV entry and intracellular trafficking to the nucleus. This review will focus on the identification of molecular components important for recombinant AAV (rAAV) transduction while highlighting the techniques used to discover them and potential clinical application of research findings.

KRIT1/cerebral cavernous malformation 1 protein localizes to vascular endothelium, astrocytes, and pyramidal cells of the adult human cerebral cortex.

OBJECTIVEMutations in KRIT1 cause familial cerebral cavernous malformation, an autosomal dominant disorder affecting primarily the central nervous system vasculature. Although recent studies have suggested that Krev-1 interaction trapped 1 (KRIT1) is a microtubule-associated protein that interacts with integrin cytoplasmic domain-associated protein-1&agr;, the function of KRIT1 remains elusive. METHODSWe used Western blotting and immunohistochemistry with specific KRIT1 polyclonal antibodies to investigate KRIT1 protein expression in diverse cerebral and extracerebral tissues. RESULTSImmunostaining demonstrates that although KRIT1 is expressed in a broad variety of human organs, it localizes to the vascular endothelium of each, specifically to capillaries and arterioles. KRIT1 antibody fails to stain fenestrated capillaries in the kidney, the liver, or the red pulp of the spleen, where endothelial cells do not to adhere to one another. In contrast, intense staining is observed in the thymus and the white pulp of the spleen, where specialized blood-organ barriers are formed. Other cell types, including various epithelia, cardiac myocytes, and hepatocytes, also stain with KRIT1. CONCLUSIONAlthough KRIT1 expression is seen in every endothelium studied, cerebral cavernous malformation lesions are seen almost exclusively in the central nervous system, suggesting that additional cell type(s) contribute to the pathophysiology of cerebral cavernous malformations. Here, we demonstrate that KRIT1 is also present in cells and structures integral to the cerebral angiogenesis and formation of the blood-brain barrier, namely, endothelial cells and astrocytic foot processes, as well as pyramidal neurons in the cerebral cortex.

Parental origin and mechanisms of formation of cytogenetically recognisable de novo direct and inverted duplications

Cytogenetic, FISH, and molecular results of 20 cases with de novo tandem duplications of 18 different autosomal chromosome segments are reported. There were 12 cases with direct duplications, three cases with inverted duplications, and five in whom determination of direction was not possible. In seven cases a rearrangement between non-sister chromatids (N-SCR) was found, whereas in the remaining 13 cases sister chromatids (SCR) were involved. Paternal and maternal origin (7:7) was found almost equally in cases with SCR (3:4) and N-SCR (4:3). In the cases with proven inversion, there was maternal and paternal origin in one case each. Twenty three out of 43 cytogenetically determined breakpoints correlated with common or rare fragile sites. In five cases, including all those with proven inverse orientation, all breakpoints corresponded to common or rare fragile sites. In at least two cases, one with an interstitial duplication (dup(19)(q11q13)) and one with a terminal duplication (dup(8) (p10p23)), concomitant deletions (del(8) (p23p23.3) and del(19)(q13q13)) were found.

Adenovirus-mediated IKKbetaKA expression sensitizes prostate carcinoma cells to TRAIL-induced apoptosis.

Despite the fact that tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) can selectively induce apoptosis in cancer cells, TRAIL resistance in cancer cells has challenged the use of TRAIL as a therapeutic agent. First, prostate carcinoma cell lines (DU145, LNCaP and PC3) were screened for sensitivity to adenovirus delivery of TRAIL (Ad5hTRAIL). As amplified Ikappa B kinase (IKK) activity is responsible for the constitutive nuclear factor-κB (NF-κB) activation leading to uncontrolled cell growth and metastasis, a dual vector approach using both an adenovirus vector (Ad) expressing the dominant-negative mutant of IKKβ (AdIKKβKA) and Ad5hTRAIL was employed to determine if prostate cancer cells were sensitized to TRAIL in the setting of IKK inhibition. Inhibition of the NF-κB pathway through IKK blockade sensitized all three prostate cancer cell lines to TRAIL, regardless of NF-κB activation or decoy receptor gene expression. Moreover, a novel quantitative real-time RT-PCR assay and conventional flow cytometry analysis indicated that TRAIL-resistant DU145 and LNCaP cells, but not TRAIL-sensitive PC3 cells, expressed substantial amounts of TRAIL Decoy Receptor 4. In conclusion, TRAIL decoy receptor expression appeared to be the chief determinant of TRAIL resistance encountered in prostate carcinoma cell lines.

Simultaneous inhibition of Rac1 and IKK pathways sensitizes lung cancer cells to TNFalpha-mediated apoptosis.

Lung cancer is the most frequently occurring cancer in the world and causes more deaths in the United States than does colon, breast, and prostate cancer combined. Despite advances in treatment modalities including radiation, surgery, and chemotherapy, the overall survival in lung cancer remains low. The cytokine tumor necrosis factor α (TNFα) has been shown to regulate both apoptotic and antiapoptotic pathways. Activation of the transcription factor NF-κB appears to be the critical determinant of the antiapoptotic response to TNFα exposure in epithelial cells. A549 human lung carcinoma cells were infected with adenoviral constructs carrying dominant negative mutants of Rac1 and IKK or constitutively active mutant of Rac1, upstream effectors in TNF-mediated NF-κB activation. Cell death, apoptosis, and NF-κB activation were subsequently measured in response to TNFα exposure. Although TNFα alone had no cytotoxic effect, the expression of the dominant negative mutant of IKKβ (Ad.IKKβKA) resulted in apoptotic cell death following TNFα exposure. Similarly, dominant negative mutant to Rac1 (Ad.N17Rac1) further sensitized A549 cells to IKKβKA-mediated TNFα-induced cell death. Conversely, a dominant active form of Rac1 (Ad.V12Rac1) ameliorated the cell death response to concurrent IKKβ dominant negative mutant infection and TNFα exposure. These results suggest that concurrent inhibition of Rac1 and IKK pathways sensitizes lung cancer cells to TNFα-induced apoptosis. Cancer Gene Therapy (2001) 8, 897–905

Molecular analysis of beta-thalassemia and sickle cell anemia in Antalya.

We have studied 918 chromosomes for mutations leading to β-thalassemia and sickle cell anemia, which are the two most frequently found monogenic disorders in Antalya, Turkey. Three hundred and seventy-seven postnatal and 82 prenatal cases were studied between 2000 and May 2003 in our center using reverse dot blot hybridization (RDBH) with 22 probes specific for Mediterranean populations. In this study, IVSI-110 (G→A) appeared to be the most common mutation with an occurrence rate of 44.4% among the 16 different mutations found to be associated with β-thalassemia. Heterozygosity for IVSI-110 was the most prevalent combination, whereas 34 of our 377 postnatal cases showed homozygosity for this mutation, a genotype leading to β-thalassemia major. The total percentage of postnatal patients clinically diagnosed as β-thalassemia major was 18.6%, whereas 5% of the cases were diagnosed clinically as β-thalassemia intermedia. One new Hb variant, Hb Antalya, and one new mutation, Cod 3 (+T) were found. HbS accounted for 10.3% of all mutations; homozygosity was found in 1.9% of all cases. Of the 82 cases analysed prenatally for β-globin gene mutations and by cytogenetic techniques for possible chromosomal abnormalities, 21 fetuses were found to be affected with β-globin gene mutations. One of these fetuses was also found to have a 45,X karyotype, and 1 had a 46,XY/47,XY,+22 karyotype. Quite a high rate of consanguineous marriages in Antalya (35.17%) renders mutation screening, genetic counseling, and educational programs held by our Thalassemia Unit essential. This study was the first to be performed specifically in our region where hemoglobinopathies are most frequent as a consequence of migrations of racially and culturally distinct groups to the area in the distant past.

Germline hMSH2 and hMLH1 gene mutations in incomplete HNPCC families.

Hereditary non‐polyposis colon cancer (HNPCC) is a common hereditary disease characterized by a predisposition to an early onset of colorectal cancer. The majority of the HNPCC families carry germline mutations of either hMSH2 or hMLH1 genes, whereas germline mutations of hPMS1 and hPMS2 genes have rarely been observed. Almost all of the germline mutations reported so far concern typical HNPCC families. However, there are families that display aggregations of colon cancer even though they do not fulfil all HNPCC criteria (incomplete HNPCC families) as well as sporadic cases of early onset colon cancers that could be related to germline mutations of these genes. Therefore, we screened germline mutations of hMSH2 and hMLH1 genes in 3 groups of patients from France and Turkey: typical HNPCC (n = 3), incomplete HNPCC (n = 9) and young patients without apparent familial history (n = 7). By in vitro synthesis of protein assay, heteroduplex analysis and direct genomic sequencing, we identified 1 family with hMSH2 mutation and 5 families with hMLH1 mutations. Two of the 3 HNPCC families (66%) displayed hMLH1 germline mutations. Interestingly, 4 of 9 families with incomplete HNPCC (44%) also displayed mutations of hMSH2 or hMLH1 genes. In contrast, no germline mutation of these genes was found in 7 young patients. Our results show that germline mutations of hMSH2 and hMLH1 genes contribute to a significant fraction of familial predisposition to colon cancer cases that do not fulfil all diagnostic criteria of HNPCC. Int. J. Cancer 73:831–836, 1997.