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Genetic analysis of the shared role of CLN3 and BCK2 at the G(1)-S transition in Saccharomyces cerevisiae.

The transcription complexes SBF and MBF mediate the G(1)-S transition in the cell cycle of Saccharomyces cerevisiae. In late G(1), SBF and MBF induce a burst of transcription in a number of genes, including G(1)- and S-phase cyclins. Activation of SBF and MBF depends on the G(1) cyclin Cln3 and a largely uncharacterized protein called Bck2. We show here that the induction of SBF/MBF target genes by Bck2 depends partly, but not wholly, on SBF and MBF. Unlike Cln3, Bck2 is capable of inducing its transcriptional targets in the absence of functional Cdc28. Our results revealed promoter-specific mechanisms of regulation by Cln3, Bck2, SBF, and MBF. We isolated high-copy suppressors of the cln3 bck2 growth defect; all of these had the ability to increase CLN2 expression. One of these suppressors was the negative regulator of meiosis RME1. Rme1 induces CLN2, and we show that it has a haploid-specific role in regulating cell size and pheromone sensitivity. Genetic analysis of the cln3 bck2 defect showed that CLN1, CLN2, and other SBF/MBF target genes have an essential role in addition to the degradation of Sic1.

Cell Cycle↗

Genetic analysis of protein kinase B (AKT) in Drosophila.

The decision between survival and death is an important aspect of cellular regulation during development and malignancy. Central to this regulation is the process of apoptosis, which is conserved in multicellular organisms [1]. A variety of signalling cascades have been implicated in modulation of apoptosis, including the phosphatidylinositol (Pl) 3-kinase pathway. Activation of Pl 3-kinase is protective, and inhibition of this lipid kinase enhances cell death under several conditions including deregulated expression of c-Myc, neurotrophin withdrawal and anoikis [2-7]. Recently, the protective effects of Pl 3-kinase have been linked to its activation of the pleckstrin homology (PH)-domain-containing protein kinase B (PKB or AKT) [8]. PKB/AKT was identified from an oncogene, v-akt, found in a rodent T-cell lymphoma [9]. To initiate a genetic analysis of PKB, we have isolated and characterized a Drosophila PKB/AKT mutant (termed Dakt1) that exhibits ectopic apoptosis during embryogenesis as judged by induction of membrane blebbing, DNA fragmentation and macrophage infiltration. Apoptosis caused by loss of Dakt function is rescued by caspase suppression but is distinct from the previously described reaper/grim/hid functions. These data implicate Dakt1 as a cell survival gene in Drosophila, consistent with cell protection studies in mammals.

Animals↗

A genetic analysis of the functions of LuxN: a two-component hybrid sensor kinase that regulates quorum sensing in Vibrio harveyi.

The bioluminescent marine bacterium Vibrio harveyi controls light production using two parallel quorum-sensing systems. V. harveyi produces two autoinducers (AI-1 and AI-2), which are recognized by cognate membrane-bound two-component hybrid sensor kinases called LuxN and LuxQ respectively. Under conditions of low cell density, in the absence of autoinducer, the hybrid sensors are kinases, and under conditions of high cell density, in the presence of autoinducer, the sensors are phosphatases. These activities allow LuxN and LuxQ to modulate the level of phosphorylation of the response regulator protein LuxO. LuxO, in turn, controls the transcription of the genes encoding luciferase. The phosphorelay protein LuxU is required for signalling to LuxO. In this report, we present a genetic analysis of the activities of the AI-1 sensor LuxN. Point mutations and in frame deletions were constructed in luxN and recombined onto the chromosome of V. harveyi for in vivo phenotypic analysis. We show that the conserved histidine (H471) in the sensor kinase domain of LuxN is required for kinase activity but not for phosphatase activity. In contrast, the conserved aspartate (D771) in the response regulator domain of LuxN is required for both activities. Furthermore, the LuxN phosphatase activity is localized to the response regulator domain. Our results indicate that the LuxN kinase activity is regulated by the presence of AI-1, whereas the LuxN phosphatase activity is constitutive. We also show that signalling from the two V. harveyi quorum-sensing systems is not equivalent. AI-1 and LuxN have a much greater effect on the level of LuxO phosphate and therefore Lux expression than do AI-2 and LuxQ.

Bacterial Proteins↗

Crystal structure combined with genetic analysis of the Thermus thermophilus ribosome recycling factor shows that a flexible hinge may act as a functional switch.

Ribosome recycling factor (RRF), in concert with elongation factor EF-G, is required for disassembly of the posttermination complex of the ribosome after release of polypeptides. The crystal structure of Thermus thermophilus RRF was determined at 2.6 A resolution. It is a tRNA-like L-shaped molecule consisting of two domains: a long three-helix bundle (domain 1) and a three-layer beta/alpha/beta sandwich (domain 2). Although the individual domain structures are similar to those of Thermotoga maritima RRF (Selmer et al., Science, 1999, 286:2349-2352), the interdomain angle differs by 33 degrees in two molecules, suggesting that the hinge between two domains is potentially flexible and responsive to different conditions of crystal packing. The hinge connects hydrophobic junctions of domains 1 and 2. The structure-based genetic analysis revealed the strong correlation between the hinge flexibility and the in vivo function of RRF. First, altering the hinge flexibility by making alanine or serine substitutions for large-size residues conserved at the hinge loop and nearby in domain 1 frequently gave rise to gain of function except a Pro residue conserved at the hinge loop. Second, the hinge defect resulting from a too relaxed hinge structure can be compensated for by secondary alterations in domain 1 that seem to increase the hydrophobic contact between domain 1 and the hinge loop. These results show that the hinge flexibility is vital for the function of RRF and that the steric interaction between the hinge loop and domains 1 and 2 restricts the interdomain angle and/or the hinge flexibility. These results indicate that RRF possesses an architectural difference from tRNA regardless of a resemblance to tRNA shape: RRF has a "gooseneck" elbow, whereas the tRNA elbow is rigid, and the direction of flex of RRF and tRNA is at a nearly right angle to each other. Moreover, surface electrostatic potentials of the two RRF proteins are dissimilar and do not mimic the surface potential of tRNA or EF-G. These properties will add a new insight into RRF, suggesting that RRF is more than a simple tRNA mimic.

Alleles↗

Capsid protein genetic analysis and viral spread to the spinal cord in cats experimentally infected with feline calicivirus (FCV).

We investigated primitively the molecular basis of the neural spread of a feline calcivirus isolate (FCV-S) from the spinal cord of a cat that died after manifesting excitation. Experimental infections of cats with three clones from parent virus isolate FCV-S, isolated based on plaque size, were performed, and virus recovery from the spinal cord and the nucleotide and predicted amino acid sequences of the viral capsid protein region (ORF2) were compared. In the experimental infection with the one-time cloned virus (C1L1) isolated from a large plaque, the C1L1 was recovered from the spinal cord. In contrast, seven-times cloned C6L7 (from large plaque) and five-times cloned C5S2 (isolated from small plaque) were not recovered from the spinal cord. Genetic analysis of the capsid protein gene of the three viral clones revealed that four bases were different and two amino acids were different at positions 34 (Val in C6L7 and Ala in C1L1 and C5S2) and 46 (Leu in C6L7 and Pro in C1L1 and C5S2) between C6L7 (with large plaque) and C5S2 (with small plaque). The amino acid at position 434 of C1L1 was different from those of C6L7 and C5S2 (Gly in C1L1, D (Asp) in C6L7 and C5S2). From these results, the plaque size seemed not to be related to the spread of virus to the spinal cord. Clone C1L1, which spread to the spinal cord, had a difference of one amino acid from the other two clones, which may be related to the ability to spread to the spinal cord.

Amino Acid Sequence↗

Genetic analysis of capsular status of meningococcal carrier isolates.

The meningococcal capsule is the primary virulence factor with systemic isolates requiring full expression of the capsule but with capability to down-regulate the capsule in order to invade. The meningococcal capsular operon is composed of a number of genes that are involved in capsular synthesis and transport. Differences in capsular synthesis genes may allow discrimination between meningococcal serogroups whereas absence of genes for either synthesis or transport imply that the meningococcus is unencapsulated. Although mechanisms such as slipped-strand mispairing and acquisition of insertion sequences have been demonstrated to be involved in regulation of capsular expression, few studies have addressed the mechanisms of capsular expression in carrier isolates. Following a community-based intervention programme for an outbreak of meningococcal disease, we collected meningococcal carrier isolates from the intervention area and control areas. We undertook genetic analysis of the capsular operon and the mechanisms of capsular regulation, together with an investigation of the potential of capsular genes to identify the genogroup of non-serogroupable isolates. Use of the siaD gene allowed the discrimination of 30/89 (34%) non-serogroupable isolates into B, C, W135 and Y with a siaA gene PCR permitting the characterization of a further 6 isolates whose capsules contained sialic acid. Slipped-strand mispairing was evident in only 4 of 13 genogroupable B isolates and the insertion sequence IS1301 was found in 2 of 36 siaA-positive isolates. Of 51 non-genogroupable isolates 25 (49%) were shown to be ctrA negative. There was a higher percentage of ctrA-positive isolates (P<0.001) amongst meningococcal strains obtained from those sampled in non-intervention schools than those sampled at intervention schools. The ctrA-negative isolates warrant further investigation of their genotypic organization since such avirulent strains may be important in conferring natural protection against invasive disease. We found that after mass antibiotic prophylaxis, recolonization occurs preferentially with non-pathogenic meningococcal strains. This as implications for assessment of the benefits of mass antibiotic and vaccination programmes for outbreak control. Previously expressed concerns of increased risk due to removal of protective ora may have been overstated.

Bacterial Capsules↗

Genetic analysis of bacterial acetyltransferases: identification of amino acids determining the specificities of the aminoglycoside 6'-N-acetyltransferase Ib and IIa proteins.

The aminoglycoside 6'-N-acetyltransferase [AAC(6')-I] and AAC(6')-II enzymes represent a class of bacterial proteins capable of acetylating tobramycin, netilmicin, and 2'-N-ethylnetilmicin. However, an important difference exists in their abilities to modify amikacin and gentamicin. The AAC(6')-I enzymes are capable of modifying amikacin. In contrast, the AAC(6')-II enzymes are capable of modifying gentamicin. Nucleotide sequence comparison of the aac(6')-Ib gene and the aac(6')-IIa gene showed 74% sequence identity (K. J. Shaw, C. A. Cramer, M. Rizzo, R. Mierzwa, K. Gewain, G. H. Miller, and R. S. Hare, Antimicrob. Agents Chemother. 33:2052-2062, 1989). Comparison of the deduced protein sequences showed 76% identity and 82% amino acid similarity. A genetic analysis of these two proteins was initiated to determine which amino acids were responsible for the differences in specificity. Results of domain exchanges, which created hybrid AAC(6') proteins, indicated that amino acids in the carboxy half of the proteins were largely responsible for determining specificity. Mutations shifting the specificity of the AAC(6')-Ib protein to that of the AAC(6')-IIa protein (i.e., gentamicin resistance and amikacin sensitivity) have been isolated. DNA sequence analysis of four independent isolates revealed base changes causing the same amino acid substitution, a leucine to serine, at position 119. Interestingly, this serine occurs naturally at the same position in the AAC(6')-IIa protein. Oligonucleotide-directed mutagenesis was used to construct the corresponding amino acid change, a serine to leucine, in the AAC(6')-IIa protein. This change resulted in the conversion of the AAC(6')-IIa substrate specificity to that of AAC(6')-Ib. Analysis of additional amino acid substitutions within this region of AAC(6')-Ib support the model that we have identified an aminoglycoside binding domain of these proteins.

Acetyltransferases↗

High-throughput genetic analysis using microfabricated 96-sample capillary array electrophoresis microplates.

Capillary array electrophoresis (CAE) microplates that can analyze 96 samples in less than 8 min have been produced by bonding 10-cm-diameter micromachined glass wafers to form a glass sandwich structure. The microplate has 96 sample wells and 48 separation channels with an injection unit that permits the serial analysis of two different samples on each capillary. An elastomer sheet with an 8 by 12 array of holes is placed on top of the glass sandwich structure to define the sample wells. Samples are addressed with an electrode array that makes up the third layer of the assembly. Detection of all lanes with high temporal resolution was achieved by using a laser-excited confocal fluorescence scanner. To demonstrate the functionality of these microplates, electrophoretic separation and fluorescence detection of a restriction fragment marker for the diagnosis of hereditary hemochromatosis were performed. CAE microplates will facilitate all types of high-throughput genetic analysis because their high assay speed provides a throughput that is 50 to 100 times greater than that of conventional slab gels.

Capillary Action↗

Streptomyces relC mutants with an altered ribosomal protein ST-L11 and genetic analysis of a Streptomyces griseus relC mutant.

Several relaxed (rel) mutants have been obtained from Streptomyces species by selecting colonies resistant to thiopeptin, an analogue of thiostrepton. Using two-dimensional gel electrophoresis, I compared the ribosomal proteins from rel and rel+ pairs of S. antibioticus, S. lavendulae, S. griseoflavus, and S. griseus. It was found that all of the Streptomyces rel mutants thus examined had an altered or missing ribosomal protein, designated tentatively ST-L11. These rel mutants therefore could be classified as relC mutants and were highly sensitive to erythromycin or high temperature. A relC mutant of S. griseus was defective in streptomycin production, but phenotypic reversion of this defect to normal productivity was found at high incidence among progeny of the relC mutant. This phenotypic reversion did not accompany a reappearance of ribosomal protein ST-L11, and furthermore the ability of accumulating ppGpp still remained at a low level, thus suggesting existence of a mutation (named sup) which suppresses the streptomycin deficiency phenotype exhibited by the relC mutant. Genetic analysis revealed that there is a correlation between the rel mutation and the inability to produce streptomycin or aerial mycelia. The sup mutation was found to lie at a chromosomal locus distinct from that of the relC mutation. It was therefore concluded that the dependence of streptomycin production on the normal function of the relC gene could be entirely bypassed by a mutation at the suppressor locus (sup). The suppressing effect of the sup mutation on the relC mutation was blocked when the afs mutation (defective in A-factor synthesis) was introduced into a relC sup double mutant. It is proposed that the sup gene or its product can be direct or indirect target for ppGpp.

Anti-Bacterial Agents↗

Chromosomal changes and correspondingly altered proto-oncogene expression in human gliomas. Value of combined cytogenetic and molecular genetic analysis.

A combined cytogenetic and molecular genetic study was performed to analyze seven primary brain tumors: one oligoastrocytoma WHO-grade II, one anaplastic astrocytoma grade III, one anaplastic astrocytoma grade III/IV and four glioblastomas by G-banding and RNA dot blotting. A normal karyotype was found in the oligoastrocytoma. One of the two anaplastic astrocytomas (male) contained cells with a normal karyotype and cells with a Y-chromosomal loss, and the other one showed structural abnormalities too complex for complete analysis in mostly polyploid cells. Two of the four glioblastomas had few and the other two multiple chromosomal changes such as +7, +20, -8, -9 del(9)(p21), -10, del(10)(q24), -13,14, del(17)(p21), -22, add(3)(q13), double minutes and marker chromosomes. Compared to normal brain, all tumors had an increased EGFr and both anaplastic astrocytomas as well as three glioblastomas a decreased H-ras expression. The two glioblastomas with multiple chromosomal changes showed increased EGFr, Ki-ras, myb, mos and myc, decreased H-ras and N-ras and unchanged levels of abl, src and sis. Both the cytogenetic and molecular genetic findings are compatible even in the case of chromosomal losses, where the genes on the remaining allele may be responsible for dominant gene regulation mechanisms which result in a protooncogene overexpression. Our findings indicate that, apart from proto-oncogene overexpression, other mechanisms, e.g. tumor suppressor gene inactivation, are important for glial tumorigenesis. Karyotypic analysis makes it possible to search specifically for genetic events still unknown but arising from particular chromosomal changes.

Adult↗

Cytochemical, immunologic, chromosomal, and molecular genetic analysis of a novel cell line derived from Hodgkin's disease.

A novel cell line, KM-H2, was established from the pleural effusion of a patient with Hodgkin's disease of mixed cellular type. Multiple phenotypic studies were carried out with this cell line. Acid phosphatase and nonspecific esterase activities were detected. Rosette formation with T lymphocytes and the receptors for C3b and Fc portion of IgG were positive. Among the antigens tested with a total of 22 monoclonal antibodies defining hematopoietic cell subsets or lineages, Ki-1, Leu-M1, MCS1, HLA-DR, and OKT9 antigens were found to be positive. The other antigens reportedly specific for T cells, B cells, natural killer (NK) cells, monocytes, interdigitating reticulum (IR) cells and dendritic reticulum cells were negative. These phenotypic features were identical to those of the Sternberg-Reed (SR) and Hodgkin (H) cells in the fresh materials reported by other researchers. Moreover, the KM-H2 cells and the parental pleural effusion cells shared several structural chromosome anomalies. These findings indicated that the KM-H2 cells are derived from the SR and H cells. Molecular genetic analysis of the KM-H2 cells disclosed that the human immunoglobulin JH gene was rearranged but not the JK gene, and that the human T cell receptor beta chain gene was of the germline type. Based on these properties of the KM-H2 cells, Hodgkin's disease may be derived from a cell lineage other than T cell or B cell.

Adult↗

Molecular genetic analysis of V-ATPase function in Drosophila melanogaster.

V-ATPases are phylogenetically widespread, highly conserved, multisubunit proton pumps. Originally characterised in endomembranes, they have been found to energise transport across plasma membranes in a range of animal cells and particularly in certain epithelia. While yeast is the model of choice for the rapid generation and identification of V-ATPase mutants, it does not allow their analysis in a plasma membrane context. For such purposes, Drosophila melanogaster is a uniquely suitable model. Accordingly, we have cloned and characterised genes encoding several V-ATPase subunits in D. melanogaster and, using P-element technology, we have succeeded in generating multiple new alleles. Reporter gene constructs reveal ubiquitous expression, but at particularly high levels in those epithelial thought to be energised by V-ATPases, and several of the alleles have lethal recessive phenotypes characterised by epithelial dysfunction. These results, while providing the first gene knockouts of V-ATPases in animals, also illustrate the general utility of D. melanogaster as a model for the genetic analysis of ion transport and its control in epithelia.

Alleles↗

The generation and genetic analysis of suppressors of lethal mutations in the Caenorhabditis elegans rol-3(V) gene.

The Caenorhabditis elegans rol-3(e754) mutation is a member of a general class of mutations affecting gross morphology, presumably through disruption of the nematode cuticle. Adult worms homozygous for rol-3(e754) exhibit rotation about their long axis associated with a left-hand twisted cuticle, musculature, gut and ventral nerve cord. Our laboratory previously isolated 12 recessive lethal alleles of rol-3. All these lethal alleles cause an arrest in development at either early or mid-larval stages, suggesting that the rol-3 gene product performs an essential developmental function. Furthermore, through the use of the heterochronic mutants lin-14 and lin-29, we have established that the expression of rol-3(e754)'s adult specific visible function is not dependent on the presence of an adult cuticle. In an attempt to understand rol-3's developmental role we sought to identify other genes whose products interact with that of rol-3. Toward this end, we generated eight EMS induced and two gamma irradiation-induced recessive suppressors of the temperature sensitive (ts) mid-larval lethal phenotype of rol-3(s1040ts). These suppressors define two complementation groups srl-1 II and srl-2 III; and, while they suppress the rol-3(s1040) lethality, they do not suppress the adult specific visible rolling phenotype. Furthermore, there is a complex genetic interaction between srl-2 and srl-1 such that srl-2(s2506) fails to complement all srl alleles tested. These results suggest that srl-1 and srl-2 may share a common function and, thus, possibly constitute members of the same gene family. Mutations in both srl-1 and srl-2 produce no obvious hermaphrodite phenotypes in the absence of rol-3(s1040ts); however, males homozygous for either srl-1 or srl-2 display aberrant tail morphology. We present evidence suggesting that the members of srl-2 are not allele specific with respect to their suppression of rol-3 lethality, and that rol-3 may act in some way to influence proper posterior morphogenesis. Finally, based on our genetic analysis of rol-3 and the srl mutations, we present a model whereby the wild-type products of the srl loci act in a concerted manner to negatively regulate the rol-3 gene.

Alleles↗

[Genetic analysis and gene deduction of powdery mildew resistance in T. durum-Ae. squarrosa amphidiploids].

Eleven seedlings with resistance and two amphidiploids with disease resistance at all developmental stage were screened by using No. 15 isolate of E. graminis f. sp. tritici to inoculate 99 T. durum-Ae. squarrosa amphidiploids. The two amphidiploids with disease resistance at all developmental stage, M53 and M81, and their Ae. squarrosa parents were resistant to No. 15 isolate of powdery mildew payhogen, but their T. durum parents were susceptible. Therefore, the powdery mildew resistance of M53 and M81 were derived from Ae. squarrosa. Amphidiploid M74, which had the same durum parent as M53 but different Ae. squrrosa parent, was susceptible to No. 15 isolate in adult stage. M29 and M35, which had the same durum parent as M81 but different Ae. squarrosa parent were susceptible in all stage. These results were also proved that the powdery mildew resistance genes were derived from Ae. sqarrosa. Genetic analysis showed that powdery mildew resistance gene in M53 or M81 was a single dominant gene. A series of lines with known powdery mildew resistance genes and two unknown lines were used to test response patterns with 14 differential isolates of E. graminis f. sp. tritici. The response patterns in M53 and M81 were different from Pm1 to Pm21 and indicated that M53 and M81 conferred a new powdery mildew resistance gene respectively.

Genes, Plant↗

[Genetic analysis of the predisposition to uterine myoma. Prevalence and morbidity].

Prevalence of uterine myoma (MU) was estimated in several Moscow districts. The overall average estimate of the MU prevalence is 2.45% among women of all groups. The prevalence MU estimates increase with the age, its maximum value reaching 8.31% at the age of 50 years. The morbidity risk estimates increased with the age as well, the maximum value being 2.98% at the age of 40-44 years. The value of "cumulative" morbidity risks, i. e. the probability to be affected, is 9.74% for a population living long enough, this value being based on the age-specific estimates of morbidity risks. Taking into consideration the autopsy data, indicating that frequency of MU, including small myomatous nodes, is 20%, the conclusion is made that MU is manifested by clinically expressed disturbances (urging a woman to address to a doctor) in 50% of cases only. Epidemiological data obtained are to be used later for genetic analysis of familial data on MU.

Adult↗

Biochemical and genetic analysis of an antigenic determinant found on N-linked oligosaccharides in Dictyostelium.

Dictyostelium discoideum synthesizes many highly immunogenic carbohydrates of unknown structure and function. We have used monoclonal antibodies prepared against one of these called CA1 to investigate its structure and the consequences of its loss. CA1 is preferentially expressed on lysosomal enzymes as a specific arrangement of mannose-6-SO4 residues on N-linked oligosaccharides. Mutant strains HL241 and HL243 do not express CA1, and synthesize a truncated lipid-linked oligosaccharide (LLO) precursor that lacks the critical mannose residues needed for expression. The lesion appears to result from the loss of mannosyl transferase activity involved in LLO biosynthesis. The truncated LLO is poorly transferred to an artificial peptide acceptor in a cell-free N-glycosylation assay, and this appears to result from improper topological localization of the LLO or to a lower affinity of the LLO for the oligosaccharyl transferase. Although both mutants share these lesions, they are biochemically and genetically distinct. Only HL243 is lower in N-glycosylation in intact cells, and this is not a result of an altered structure of the LLO. There are other differences between the strains. HL241 can form fruiting bodies at a slower rate than normal while HL243 cannot aggregate. Genetic analysis of defects shows that the CA1 lesion in HL241 is recessive, while the lesion in both CA1 and in development are dominant and co-segregate in HL243 and are, therefore, likely to be in the same gene. Lysosomal enzyme targeting is normal but enzyme processing proceeds at a 2-3 fold slower rate in HL241 and HL243 compared to wild-type. Strain HL244 does not express CA1 since it completely lacks protein sulfation, but lysosomal enzyme targeting and processing proceeds at a normal rate, showing that sulfate is not essential for these processes. Alterations in oligosaccharide structure can have individualized effects on the biosynthesis of lysosomal enzymes. The results presented here illustrate how this approach can be used to study both the structure and function of carbohydrate epitopes.

Acid Phosphatase↗

Genetic analysis of yeast Yip1p function reveals a requirement for Golgi-localized rab proteins and rab-Guanine nucleotide dissociation inhibitor.

Yip1p is the first identified Rab-interacting membrane protein and the founder member of the YIP1 family, with both orthologs and paralogs found in all eukaryotic genomes. The exact role of Yip1p is unclear; YIP1 is an essential gene and defective alleles severely disrupt membrane transport and inhibit ER vesicle budding. Yip1p has the ability to physically interact with Rab proteins and the nature of this interaction has led to suggestions that Yip1p may function in the process by which Rab proteins translocate between cytosol and membranes. In this study we have investigated the physiological requirements for Yip1p action. Yip1p function requires Rab-GDI and Rab proteins, and several mutations that abrogate Yip1p function lack Rab-interacting capability. We have previously shown that Yip1p in detergent extracts has the capability to physically interact with Rab proteins in a promiscuous manner; however, a genetic analysis that covers every yeast Rab reveals that the Rab requirement in vivo is exclusively confined to a subset of Rab proteins that are localized to the Golgi apparatus.

COP-Coated Vesicles↗

Genetic analysis in patients with left ventricular noncompaction and evidence for genetic heterogeneity.

Left ventricular noncompaction (LVNC) is a cardiomyopathy characterized by numerous excessively trabeculations and deep intertrabecular recesses. This study was performed to investigate Japanese LVNC patients for disease-causing mutations in a series of selected candidate genes. DNA was isolated from the peripheral blood of 79 cases including 20 familial cases and 59 sporadic cases. DNA samples were screened for mutations in the genes encoding G4.5 (TAZ), alpha-dystrobrevin (DTNA), alpha1-syntrophin (SNTA1), FK506 Binding protein 1A (FKBP1A or FKPB12: FKBP1A), and LIM Domain Binding protein 3 (Cypher/ZASP: LDB3), using single-strand conformational polymorphism analysis and DNA sequencing. DNA variants were identified in 6 of the 79 cases, including four familial cases and two sporadic cases. A splice acceptor mutation of intron 8 in TAZ (IVS8-1G>C) was identified in one family with isolated LVNC, resulting in deletion of exon 9 from mRNA. In a sporadic case of isolated LVNC and Barth syndrome (BTHS), a 158insC in exon 2 of TAZ resulting in a frame-shift mutation was identified. A 1876G>A substitution changing an aspartic acid to asparagine (D626N) was identified in LDB3 in four members of two families with LVNC. A 163G>A polymorphism was identified in LDB3, which changed a valine to isoleucine (V55I) in one patient with isolated LVNC. In addition, in a family with nonisolated LVNC, a 362C>T mutation was identified in DTNA. LVNC, like other forms of inherited cardiomyopathy, is a genetically heterogeneous disease, associated with variable clinical symptoms and can be inherited as an autosomal or X-linked recessive disorder.

Acyltransferases↗