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.

Human MYO15A is located on chromosome 17p11.2, has 66 exons and encodes unconventional myosin XVA. Recessive mutations of MYO15A are associated with profound, nonsyndromic hearing loss DFNB3 in humans, and deafness and circling behavior in shaker 2 mice. In the inner ear, this motor protein is necessary for the development of hair cell stereocilia, which are actin-filled projections on the apical surface and the site of mechanotransduction of sound. The longest isoform of myosin XVA has 3,530 amino acid residues. Two isoform classes of MYO15A are distinguished by the presence or absence of 1,203 residues preceding the motor domain encoded by alternatively-spliced exon 2. It is not known whether this large N-terminal extension of myosin XVA is functionally necessary for hearing. We ascertained approximately 600 consanguineous families segregating hereditary hearing loss as a recessive trait and found evidence of linkage of markers at the DFNB3 locus to hearing loss in 38 of these families ascertained in Pakistan (n=30), India (n=6), and Turkey (n=2). In this study, we describe 16 novel recessive mutations of MYO15A associated with severe to profound hearing loss segregating in 20 of these DFNB3-linked families. Importantly, two homozygous mutant alleles-c.3313G>T (p.E1105X) and c.3334delG (p.G1112fsX1124) of MYO15A-located in exon 2 are associated with severe to profound hearing loss segregating in two families. These data demonstrate that isoform 1, containing the large N-terminal extension, is also necessary for normal hearing.

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.

PTEN (phosphatase and tensin homolog deleted on chromosome 10) is a tumor suppressor gene, mutated frequently in a variety of human tumors. PTEN regulates cell growth, apoptosis, and proliferation. Phosphorylation in PTEN tail causes its inactivation and decreases its degradation. There is little known about the regulation of PTEN by ovarian steroids. We hypothesized that PTEN expression in human endometrium is variable throughout the menstrual cycle and early pregnancy, and that ovarian steroids regulate PTEN expression because PTEN is critical in many steroid-sensitive tissues such as endometrium, prostate, and breast. In the present study, we have observed a direct regulation of PTEN by ovarian steroids. Estradiol increased PTEN phosphorylation at 5-15 min. After 24-h treatment, progesterone induced a significant increase in PTEN protein levels, assessed by Western blot. Furthermore, we evaluated for the first time a comparison between menstrual cycle and early pregnancy, immunohistochemically. Endometrial PTEN expression revealed temporal and spatial changes throughout the menstrual cycle and during early pregnancy. We conclude that estradiol may down-regulate PTEN activity by increasing its phosphorylation, but progesterone is likely to regulate the PTEN pool by decreasing its phosphorylation and increasing its protein level. Presented data, therefore, suggest that ovarian steroids regulate the endometrial PTEN pool. We propose that PTEN might be one of the signaling proteins that estrogen and progesterone are acting to affect endometrial cell proliferation and/or apoptosis.

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.