Browsing by Subject "genetics"

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    ATPase and Multidrug Transport Activities of the Overexpressed Yeast ABC Protein Yor1p
    (1998) Decottignies, Anabelle; Grant, Althea M; Nichols, J Wylie; de Wet, Heidi; McIntosh, David B; Goffeau, André
    The Saccharomyces cerevisiae genome encodes 15 full-size ATP binding cassette transporters (ABC), of which PDR5, SNQ2, and YOR1 are known to be regulated by the transcription factors Pdr1p and Pdr3p (pleiotropic drug resistance). We have identified two new ABC transporter-encoding genes, PDR10 and PDR15, which were up-regulated by the PDR1-3 mutation. These genes, as well as four other ABC transporter-encoding genes, were deleted in order to study the properties of Yor1p. The PDR1-3 gain-of-function mutant was then used to overproduce Yor1p up to 10% of the total plasma membrane proteins. Overexpressed Yor1p was photolabeled by [gamma-32P]2', 3'-O-(2,4,6-trinitrophenyl)-8-azido-ATP (K0.5 = 45 microM) and inhibited by ATP (KD = 0.3 mM) in plasma membranes. Solubilization and partial purification on sucrose gradient allowed to detect significant Yor1p ATP hydrolysis activity (approximately 100 nmol of Pi.min-1.mg-1). This activity was phospholipid-dependent and sensitive to low concentrations of vanadate (I50 = 0.3 microM) and oligomycin (I50 = 8.5 microg/ml). In vivo, we observed a correlation between the amount of Yor1p in the plasma membrane and the level of resistance to oligomycin. We also demonstrated that Yor1p drives an energy-dependent, proton uncoupler-insensitive, cellular extrusion of rhodamine B. Furthermore, cells lacking both Yor1p and Pdr5p (but not Snq2p) showed increased accumulation of the fluorescent derivative of 1-myristoyl-2-[6-(NBD)aminocaproyl]phosphatidylethanolamine. Despite their different topologies, both Yor1p and Pdr5p mediated the ATP-dependent translocation of similar drugs and phospholipids across the yeast cell membrane. Both ABC transporters exhibit ATP hydrolysis in vitro, but Pdr5p ATPase activity is about 15 times higher than that of Yor1p, which may indicate mechanistic or regulatory differences between the two enzymes.
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    Investigating genetic variants present in a sudden unexpected death of an infant case through molecular autopsy and co-segregation analysis
    (2026) Mostert, Suné; Heathfield, Laura; Abrahams, Shameemah
    Sudden, unexpected deaths must undergo a post-mortem investigation according to South African legislation. Unfortunately, there remain cases where, even after the post-mortem investigation, the cause of death cannot be determined. One hypothesis is that the cause of death is due to molecular changes caused by genetic variants, which cannot be detected using conventional methods. We, therefore, performed a systematic literature review to identify some of these genetic variants associated with sudden unexpected death in infant cases with African ancestry. We looked at some of the disease phenotypes associated with these genetic variants as well as the genetic methods used when performing these assessments. We identified 43 variants in 14 cardiac genes, 16 variants in eight genes previously associated with neurological disorders, and four variants in four genes related to the metabolic system. Finally, we investigated a sudden unexpected death of an infant case using a molecular autopsy. The clinical exomes of the infant and parents were sequenced using the Illumina TruSight One panel for ~4800 genes. After filtering for quality, variants were prioritised, which resulted in 14 variants where pathogenicity was assessed using the American College of Medical Genetics and Genomics and the Association for Molecular Pathology criteria. Five of these variants were of interest within the case context and were thus confirmed in the proband using Sanger sequencing, and segregation analysis was carried out using parental DNA. However, all five of these variants were of unknown significance. Assigning pathogenicity to variants can prove incredibly difficult and time-consuming with limited functional analysis and limited case information, as was proved by this case study. Although the molecular autopsy provides valuable insight and can aid in case investigation, there are currently crucial gaps in the extensive amount of variants that are currently being reported and their interpretation. Furthermore, due to the complex nature of this case, which includes the infant's prematurity, low birth weight, lower respiratory tract infection, and antiretroviral therapy, it would be difficult to confidently link any genetic variant with the cause of death.
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    Morphological and genetic differentiation of Patella granularis (Gastropoda: Patellidae): recognition of two sibling species along the coast of southern Africa.
    (Wiley, 1998) Ridgway, T; Stewart, B; Branch, G; Hodgson, A
    Morphological and isozyme variations between 13 populations of the species hitherto named Patella granularis were investigated to see whether differences in shell structure between the west coast versus the south and east coasts of southern Africa are supported by other morphological features or by genetic differences. The shells showed a de®nite decrease in size from west to east, but this is correlated with productivity and is of no diagnostic use in distinguishing between populations. Discriminant functions analysis based on shell morphometrics failed to separate populations from the three coastal regions. Shells from the northern east coast do, however, have shell nodules with a dark pigmentation, distinctly separating them from those further south and west. No differences in radular or soft part morphology were detected between the populations, but the four northernmost populations on the east coast have a signi®cantly shorter Z looping of the gut than the other populations along the coast. Signi®cant microstructural differences in the sperm were also detected between these two groups of populations. Electrophoretic analysis of 16 enzyme loci failed to detect any signi®cant differences between the west and south coast populations, but revealed a genetic identity (Nei) of 0.528 as well as four diagnostic alleles between the four northernmost populations from the east coast compared with those to the south and west. The two genetically distinct forms occurred sympatrically at one of the study sites on the east coast (Coffee Bay). It was concluded the two groupings were suf®ciently different to warrant the recognition of a separate species, which is centred in KwaZulu-Natal on the east coast and extends south to Coffee Bay, from where it is replaced by P. granularis. There is, however, no evidence at all that the west coast populations are in any way separable from the remaining populations of P. granularis on the south coast.