Identification and characterization of HAOX1, HAOX2, and HAOX3, three human peroxisomal 2-hydroxy acid oxidases

Computer-based approaches identified three distinct human 2-hydroxy acid oxidase genes, HAOX1, HAOX2, and HAOX3, that encode proteins with significant sequence similarity to plant glycolate oxidase, a prototypical 2-hydroxy acid oxidase. The products of these genes are targeted to peroxisomes and have 2-hydroxy acid oxidase activities. Each gene displays a distinct tissue-specific pattern of expression, and each enzyme exhibits distinct substrate preferences. HAOX1 is expressed primarily in liver and pancreas and is most active on the two-carbon substrate, glycolate, but is also active on 2-hydroxy fatty acids. HAOX2 is expressed predominantly in liver and kidney and displays highest activity toward 2-hydroxypalmitate. HAOX3 expression was detected only in pancreas, and this enzyme displayed a preference for the medium chain substrate 2-hydroxyoctanoate. These results indicate that all three human 2-hydroxy acid oxidases are involved in the oxidation of 2-hydroxy fatty acids and may also contribute to the general pathway of fatty acid alpha-oxidation. Primary hyperoxaluria type 1 (PH1) is caused by defects in peroxisomal alanine-glyoxylate aminotransferase, the enzyme that normally eliminates intraperoxisomal glyoxylate. The presence of HAOX1 in liver and kidney peroxisomes and the ability of HAOX1 to oxidize glyoxylate to oxalate implicate HAOX1 as a mediator of PH1 pathophysiology.

The mouse neurological mutant flailer expresses a novel hybrid gene derived by exon shuffling between Gnb5 and Myo5a

Exon shuffling is thought to be an important mechanism for evolution of new genes. Here we show that the mouse neurological mutation flailer (flr) expresses a novel gene that combines the promoter and first two exons of guanine nucleotide binding protein beta 5 (Gnb5) with the C-terminal exons of the closely linked Myosin 5A (MyoVA) gene (Myo5a). The flailer protein, which is expressed predominantly in brain, contains the N-terminal 83 amino acids of Gnb5 fused in-frame with the C-terminal 711 amino acids of MyoVA, including the globular tail domain that binds organelles for intracellular transport. Biochemical and genetic studies indicate that the flailer protein competes with wild-type MyoVA in vivo, preventing the localization of smooth endoplasmic reticulum vesicles in the dendritic spines of cerebellar Purkinje cells. The flailer protein thus has a dominant-negative mechanism of action with a recessive mode of inheritance due to the dependence of competitive binding on the ratio between mutant and wild-type proteins. The chromosomal arrangement of Myo5a upstream of Gnb5 is consistent with non-homologous recombination as the mutational mechanism. To our knowledge, flailer is the first example of a mammalian mutation caused by germ line exon shuffling between unrelated genes.

Ethnic minority psychology in the 20th century: reflections and meditations on what has been and what is next

The launching of a new journal on ethnic minority psychology is placed in the context of events of the 20th century that precede it and make it possible. Citing the Dulles conference in 1978 on the role of ethnic minority issues in psychology, the author describes how the creation of the American Psychological Association (APA's) Office of Ethnic Minority Affairs and related governance structures made the creation of APA Division 45 (Society for the Psychological Study of Ethnic Minority Issues) possible, and hence their journal, Cultural Diversity and Ethnic Minority Psychology. Issues of conflict and cooperation among ethnic minority groups are discussed as the challenge to create unity from diversity is faced. Consideration of the steady increase in doctorally trained ethnic minority psychologists, relevant research, and organizational structures provides a basis for a publication outlet for these ideas. The challenges for ethnic minority psychology in the 21st century include research on the cultural diversity underlying ethnic minority groups and the similarities revealed by these differences, as well as the differences themselves. The new journal must fulfill the broad promise of the psychological study of ethnic minority issues on which Division 45 was founded.

PEX19 binds multiple peroxisomal membrane proteins, is predominantly cytoplasmic, and is required for peroxisome membrane synthesis

Peroxisomes are components of virtually all eukaryotic cells. While much is known about peroxisomal matrix protein import, our understanding of how peroxisomal membrane proteins (PMPs) are targeted and inserted into the peroxisome membrane is extremely limited. Here, we show that PEX19 binds a broad spectrum of PMPs, displays saturable PMP binding, and interacts with regions of PMPs required for their targeting to peroxisomes. Furthermore, mislocalization of PEX19 to the nucleus leads to nuclear accumulation of newly synthesized PMPs. At steady state, PEX19 is bimodally distributed between the cytoplasm and peroxisome, with most of the protein in the cytoplasm. We propose that PEX19 may bind newly synthesized PMPs and facilitate their insertion into the peroxisome membrane. This hypothesis is supported by the observation that the loss of PEX19 results in degradation of PMPs and/or mislocalization of PMPs to the mitochondrion.

Using videotaped specimens to test quality control in a computer-assisted semen analysis system

OBJECTIVE

To determine the feasibility of using semen samples previously recorded on videotape for intralaboratory and interlaboratory quality control of computer-assisted semen analysis (CASA) systems.

DESIGN

Blinded, controlled study.

SETTING

Pooled semen specimens from two normal human volunteers in an academic research environment.

PATIENT(S)

None.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Semen parameters from a videotape analyzed internally and by four external laboratories.

RESULT(S)

Preliminary experiments designed to examine intralaboratory variation by repeated analysis of semen samples recorded on videotape revealed some significant differences for every variable examined. When these data were analyzed by using the larger biologic error caused by subsampling, no significant differences were found for any of the variables examined. When either a standard set or the specific laboratories' sets of parameters were used to analyze the same videotaped semen specimen, no statistically significant differences were detected for sperm concentration for motility among the five laboratories after the biological error caused by subsampling was applied to results.

CONCLUSION(S)

These data strongly suggest that videotaped semen specimens can serve as quality control for intralaboratory and interlaboratory testing of CASA equipment as long as the biologic error caused by subsampling is used to compare results.

A prospective study of primary care patients with musculoskeletal pain: the identification of predictive factors for chronicity

Primary care faces the challenge of reducing the proportion of patients continuing with musculoskeletal pain beyond the acute phase. This study assessed patients presenting in general practice with a four- to 12-week history of pain and re-assessed them 12 weeks later. Patients whose pain was described as 'none' or 'slight' were allocated to the 'acute group', and those whose pain continued to be 'moderate' or 'severe' were allocated to the 'chronic group'. Comparative analysis of the two groups' responses at initial assessment identified pain intensity, active coping score, and previous pain episode to be factors independently predictive of chronicity.

Using the metabolism of PAHs in a human cell line to characterize environmental samples

P450 reporter gene system (RGS) is an in vitro assay to detect compounds that activate the Ah receptor and induce cytochrome P450 (CYP1A1). This system utilizes a human cell (101L) stably transfected with a luciferase reporter downstream of human CYP1A1 promoter sequences. When CYP1A1-inducing compounds are present, luciferase is produced as well as endogenous CYP1A1 enzymes. Polycyclic aromatic hydrocarbons (PAHs) are more readily degraded than chlorinated compounds including dioxins, furans, and coplanar polychlorinated biphenyls (PCBs). PAH-induced luciferase production begins to decrease between 6 and 16 h, while chlorinated compounds produce a more sustained response. Individual and mixtures of CYP1A1-inducing compounds were tested at both 6 and 16 h. Extracts of soils containing both PAHs and dioxins were also tested, before and after cleanup to remove PAHs. Results indicate that RGS testing at 6 and 16 h is a promising tool to differentiate between PAHs and chlorinated hydrocarbons often co-occurring in environmental samples.

Great pains: famous people with headaches

Have headaches influenced the course of history? It is very difficult to prove, but there is no doubt that head pains have affected some of the most influential people in history. This review explores how headaches have affected some of the world's most famous people.

Duplex opening by primosome protein PriA for replisome assembly on a recombination intermediate

PriA and other primosome assembly proteins of Escherichia coli recruit the major replicative helicase DnaB for replisome assembly during bacteriophage Mu transposition and replication. MuA transposase catalyzes the transfer of Mu ends to target DNA, forming a potential replication fork that provides the assembly site for the replisome. However, this fork lacks the single-stranded DNA needed to load DnaB. Although no pre-existing primosome assembly sites that bind PriA were found within the Mu end sequences, PriA was able to bind to the forked DNA structure created by MuA. The helicase activity of PriA could then open the duplex to create the DnaB binding site. In a tightly coupled reaction on synthetic forked substrates, PriA promoted both the unwinding of the lagging strand arm and preprimosome assembly to load DnaB onto the lagging strand template. PriA apparently translocated 3' to 5' along the lagging strand template until sufficient single-stranded DNA was exposed for binding of DnaB, which then translocated 5' to 3' in the opposite direction. Mutant PriA lacking helicase activity was unable to promote this process, and loss of PriA helicase impaired Mu DNA replication in vivo and in vitro. This suggests that the opening of the duplex by PriA helicase is a critical step in the initiation of Mu DNA replication. Concerted helicase and primosome assembly functions would allow PriA to act as initiator on recombination intermediates and stalled replication forks. As part of the replisome, PriA may act as a mobile initiator that minimizes interruptions in chromosomal replication.

Identification of peroxisomal acyl-CoA thioesterases in yeast and humans

A computer-based screen of the Saccharomyces cerevisiae genome identified YJR019C as a candidate oleate-induced gene. YJR019C mRNA levels were increased significantly during growth on fatty acids, suggesting that it may play a role in fatty acid metabolism. The YJR019C product is highly similar to tesB, a bacterial acyl-CoA thioesterase, and carries a tripeptide sequence, alanine-lysine-phenylalanineCOOH, that closely resembles the consensus sequence for type-1 peroxisomal targeting signals. YJR019C directed green fluorescence protein to peroxisomes, and biochemical studies revealed that YJR019C is an abundant component of purified yeast peroxisomes. Disruption of the YJR019C gene caused a significant decrease in total cellular thioesterase activity, and recombinant YJR019C was found to exhibit intrinsic acyl-CoA thioesterase activity of 6 units/mg. YJR019C also shared significant sequence similarity with hTE, a human thioesterase that was previously identified because of its interaction with human immunodeficiency virus-Nef in the yeast two-hybrid assay. We report here that hTE is also a peroxisomal protein, demonstrating that thioesterase activity is a conserved feature of peroxisomes. We propose that YJR019C and hTE be renamed as yeast and human PTE1 to reflect the fact that they encode peroxisomal thioesterases. The physical segregation of yeast and human PTE1 from the cytosolic fatty acid synthase suggests that these enzymes are unlikely to play a role in formation of fatty acids. Instead, the observation that PTE1 contributes to growth on fatty acids implicates this thioesterase in fatty acid oxidation.

Heterozygosity of p21WAF1/CIP1 enhances tumor cell proliferation and cyclin D1-associated kinase activity in a murine mammary cancer model

The p21(WAF1/cIP1) cyclin-dependent kinase (cdk) inhibitor is a regulator of the G(1)-S cell cycle checkpoint. Despite the importance of p21 in cell cycle inhibition, its role as a tumor suppressor is uncertain. p21 mutations are infrequent in human tumors, and p21 null mice exhibit no increased tumor incidence. To ascertain whether p21 could influence tumor formation or progression in the context of other oncogenic stimuli, we crossed p21-deficient mice with mammary tumor susceptible Wnt-1 transgenic mice. The p21+/+, p21+/-, and p21-/- Wnt-1 transgenic female offspring were monitored for mammary tumor incidence and growth rates. p21 status had no effect on the age at which mammary tumors formed. However, p21+/- mammary tumors grew significantly faster than p21+/+ and p21-/- mammary tumors. The increased growth rates were confirmed by mitotic index counts and by BrdUrd labelling assays, indicating that a significantly higher percentage of p21+/- tumor cells were in S phase and mitosis than their p21+/+ and p21-/- counterparts. Moreover, cyclin D1-associated phosphorylation of retinoblastoma protein was significantly increased in p21+/- tumor lysates compared with p21+/+ and p21-/- lysates. These results are consistent with data indicating that reduced levels of p21 can facilitate cyclin/cdk complex formation while enhancing cdk activity. Thus, a reduction of p21 dosage may promote tumor progression in the presence of other oncogenic initiators. The dependence of p21 on prior oncogenic stimuli for its tumor-promoting activities suggests that it may behave as a tumor modifier gene rather than as a tumor suppressor gene.

Relative potencies of PAHs and PCBs based on the response of human cells

P450 reporter gene system (RGS) utilizes a human hepatoma cell line stably transfected with a plasmid containing firefly luciferase linked to human CYP1A1 promoter sequences. Luciferase expression in these cells is used to detect and quantify compounds that activate the Ah receptor (AhR) and induce CYP1A1. In this study, concentration-response curves were used to determine the relative potencies and calculate induction equivalency factors (IEFs) for non-ortho and mono-ortho coplanar PCBs and high-molecular weight PAHs. Relative potencies of PCBs were: 3,4,4',5-TetraCB (81)>3,3',4,4',5-PentaCB (126)>3,3',4,4'-TetraCB (77)≈2,3,4,4',5-PentaCB (114)>2,3',4,4',5-PentaCB (118)≈2',3,4,4',5-PentaCB (123)>3,3',4,4',5,5'-HexaCB (169). In addition, two other mono-ortho congeners, 2,3,3',4,4'-PentaCB (105) and 2,3,3',4,4',5-HexaCB (156), did not induce luciferase in these cells. Relative potencies of the PAHs were: benzo[k]fluoranthene>dibenz[a,h]anthracene>benzo[b]fluoranthene≈indeno[1,2,3-cd]pyrene>benzo[a]pyrene>chrysene≈benzo[a]anthracene>benzo[g,h,i]perylene. Relative potencies of PAHs are similar to those of PCBs.

Exon organization, coding sequence, physical mapping, and polymorphic intragenic markers for the human neuronal sodium channel gene SCN8A

The voltage-gated sodium channel SCN8A is associated with inherited neurological disorders in the mouse that include ataxia, dystonia, severe muscle weakness, and paralysis. We report the complete coding sequence and exon organization of the human SCN8A gene. The predicted 1980 amino acid residues are distributed among 28 exons, including two pairs of alternatively spliced exons. The SCN8A protein is evolutionarily conserved, with 98.5% amino acid sequence identity between human and mouse. Consensus sites for phosphorylation of serine/threonine and tyrosine residues are present in cyoplasmic loop domains. The polymorphic (CA)n microsatellite marker D12S2211, with PIC = 0.68, was isolated from intron 10C of SCN8A. Single nucleotide polymorphisms in intron 19 and exon 22 were also identified. We localized SCN8A to chromosome band 12q13.1 by physical mapping on a YAC contig. The cDNA clone CSC-1 was reported by others to be a cardiac-specific sodium channel, but sequence comparison demonstrates that it is derived from exon 24 of human SCN8A. The genetic information described here will be useful in evaluating SCN8A as a candidate gene for human neurological disease.

Embryonic stem cell lines derived from human blastocysts

Human blastocyst-derived, pluripotent cell lines are described that have normal karyotypes, express high levels of telomerase activity, and express cell surface markers that characterize primate embryonic stem cells but do not characterize other early lineages. After undifferentiated proliferation in vitro for 4 to 5 months, these cells still maintained the developmental potential to form trophoblast and derivatives of all three embryonic germ layers, including gut epithelium (endoderm); cartilage, bone, smooth muscle, and striated muscle (mesoderm); and neural epithelium, embryonic ganglia, and stratified squamous epithelium (ectoderm). These cell lines should be useful in human developmental biology, drug discovery, and transplantation medicine.

A re-audit of pulmonary function laboratories in the West Midlands

In 1991 the West Midlands Pulmonary Function Audit Group examined the consistency between pulmonary function laboratories in the West Midlands. Three healthy subjects visited 22 centres and performed a standard set of pulmonary function tests. Demographic data on nine hypothetical subjects was also supplied for the laboratories to produce predicted values. Equipment was checked for accuracy using standard methods. The 1991 audit revealed significant inter-laboratory variability. Sources of error were identified and after consultation, recommendations were made to improve consistency. In addition, national and regional training workshops were organized for laboratory staff. In 1995 the audit was repeated using the same three subjects. Significant differences continued for all predicted results except for residual volume (RV) and forced vital capacity (FVC) and for all measured results except for functional residual capacity (FRC). However, improvements in the coefficient of variation were seen compared with 1991 for predicted forced expiratory volume (FEV1), total lung capacity (TLC), gas transfer (TLCO), FVC, FRC and RV. Similar improvements were seen in measured results for FEV1 and FVC. Increased variation was seen for predicted corrected transfer factor (KCO) and actual RV. The majority of variables in the 1995 audit had a coefficient of variation of less than 5% between laboratories. Analysis of the predicted results from the hypothetical subjects continued to show unacceptable variation reflecting continuing computer algorithm inconsistency. The improvements seen are encouraging and suggest that a regular audit programme is worthwhile.

Effects of hypervolemia and hypovolemia on cardiac and posterior lymph heart function in the toad Bufo marinus (L.)

Cardiac and posterior lymph heart function in the toad Bufo marinus (L.) were measured in response to hemorrhage and both systemic and lymphatic volume loading to evaluate the role of the amphibian lymphatic system in fluid regulation. In every animal, systemic volume loading elicited an initial sharp rise in mean arterial blood pressure, corresponding to an immediate cessation of lymph heart contraction lasting approximately 12 min. This was followed by a short-term decrease in blood pressure, to 36% below normal. While stroke volume and lymph flow for the individual animals increased variably over a 6-h period, mean lymph heart rate and pressure varied little. Lymphatic volume loading elicited only minor changes in blood heart and lymph heart rate. Again, stroke volume and lymph flow increased variably, with the effect lasting about 13 h. Hypovolemia caused a sharp drop in blood pressure and a corresponding rise in blood heart rate. Lymph heart variables changed little, with the exception of rate, which, in some animals, was elevated for approximately 20 min following hemorrhage.

6-hydroxydopamine lesion of rat nigrostriatal dopaminergic neurons differentially affects nicotinic acetylcholine receptor subunit mRNA expression

Nicotinic acetylcholine receptor (nAChR) subunit mRNA expression in the rat substantia nigra (SN) was assayed by semiquantitative RT-PCR following 6-hydroxydopamine (6-OHDA) lesion of nigrostriatal dopaminergic neurons. Six months after unilateral injection of 6-OHDA or saline into the SN, total RNA was isolated from ipsilateral and contralateral tissue samples. RT-PCR amplifications were performed with template titration using primers specific for sequences encoding 1. nAChR alpha 2-alpha 7 and beta 2-beta 4 subunits 2. Glutamic acid decarboxylase 3. Glyceraldehyde 3-phosphate dehydrogenase for normalization of template mass. PCR products specific for alpha 3, alpha 4, alpha 5, alpha 6, alpha 7, beta 2, beta 3, and glutamic acid decarboxylase were detected in the reactions containing SN RNA. This is the first evidence that alpha 7 may be expressed in the SN. alpha 2 and beta 4 PCR products were not detected in SN reactions, although they were observed in hippocampus and thalamus control reactions. A comparison of ipsilateral and contralateral SN RT-PCR reaction products showed substantial decreases in alpha 5, alpha 6, and beta 3 product yields following 6-OHDA, but not sham treatment. Neither the SN of sham-lesioned rats nor the thalamus of 6-OHDA-lesioned rats yielded similar results, indicating that the effects observed in 6-OHDA-treated SN were not caused by local mechanical damage or a nonspecific response, respectively. Effects of 6-OHDA treatment on alpha 3, alpha 4, alpha 7, beta 2, or glutamic acid decarboxylase product yields from SN samples were small or undetectable. The results suggest that alpha 5, alpha 6, and beta 3 subunit-encoding mRNAs are expressed at substantially higher levels in dopaminergic than in nondopaminergic cell bodies in the SN.

Calcium channel beta 4 (CACNB4): human ortholog of the mouse epilepsy gene lethargic

The mouse neurological mutant lethargic (lh) is characterized by ataxia, focal myoclonus, and absence epilepsy due to a loss-of-function mutation in the beta4 subunit of the voltage-gated calcium channel. To evaluate the role of this channel subunit in human neurological disease, we determined the chromosomal location and intron/exon structure of the human CACNB4 gene. The 1560-bp open reading frame of the CACNB4 cDNA predicts a 58-kDa protein with an amino acid sequence that is 99% identical to the rat protein. The 13 coding exons of CACNB4 span >55 kb of genomic DNA. Human cerebellar RNA contains one major CACNB4 transcript that is 9 kb in length. Expression of CACNB4 was detected in cerebellum, kidney, testis, retina, lymphoblasts, and circulating lymphocytes. Retinal transcripts were localized by in situ hybridization to ganglion cells and the inner nuclear layer. Analysis of the GeneBridge 4 radiation hybrid mapping panel localized CACNB4 to position 791 cR on human chromosome 2, in a conserved linkage group on human 2q22-q31 and mouse chromosome 2. We localized CACNB4 to the 1.3-Mb YAC clone 952F10 in Whitehead contig WC861, along with the polymorphic markers D2S2236 and D2S2299. The chromosomal linkage of three of the four beta subunit genes to homeobox gene clusters associates the evolutionary origin of the beta gene family with the events that generated the four HOX clusters early in vertebrate evolution.

Pax2 expression and retinal morphogenesis in the normal and Krd mouse

The Kidney and retinal defects (Krd) mouse carries a 7-cM transgene-induced deletion on chromosome 19 that includes the Pax2 locus. Adult mice heterozygous for the Krd deletion (Krd/+) are haploid for Pax2 and have a variable, semidominant phenotype characterized by structural defects of the kidney, retina, and optic disc. Renal and ocular anomalies present in heterozygous Pax2 mutants in both mice and humans support the hypothesis that haploinsufficiency of Pax2 underlies the Krd phenotype. To understand the embryonic basis of ocular defects observed in adult Krd/+ mice, we used immunohistochemistry, digital three-dimensional reconstructions, and quantitative morphometry to examine Pax2 protein distribution and ocular development in normal and Krd/+ mice from E10.5 to P2. In +/+ embryos, Pax2 immunopositive (Pax2+) cells demarcate the embryonic fissure as it forms in the ventral optic cup and optic stalk. After closure of the embryonic fissure, Pax2 immunostaining disappears from the ventral retina, but persists in a cuff of cells encircling the developing optic disc, the site where ganglion cell axons exit the retina. In Krd/+ embryos, Pax2+ cells in the posterior optic cup and the optic stalk undergo abnormal morphogenetic movements and the embryonic fissure fails to form normally. This results in an abnormal organization of the Pax2+ cells and ganglion cell axons at the nascent optic disc. The abnormal morphogenetic movements of the Pax2+ cells in the embryonic retina and optic stalk and the initial misrouting of the ganglion cell axons give rise to retinal and optic disc defects observed in the adult Krd/+ mice.