EVALUATION OF PAIN-KILLING ACTION OF ACETYLSALICYLIC ACID NANOPARTICLES ON THERMAL NOCICEPTION IN MICE

Pain is a common experience that can range from mild annoyance to debilitating agony. As such, finding effective ways to relieve pain is a crucial aspect of healthcare. Aspirin, a nonsteroidal anti-inflammatory drug (NSAID), is a commonly used analgesic that works by inhibiting the production of prostaglandins, which are responsible for causing pain. However, the effectiveness of aspirin can be influenced by various factors, including the form in which it is administered. The current study aimed to compare the effects of aspirin's ordinary particles and nanoparticles as an analgesic utilizing the hot plate method in topical formulations (gel, ointment, cream). The study employed 120 albino mice, all males, divided into six groups. In the three groups, aspirin was topically applied using various formulations (gel, cream, and ointment, respectively) and concentrations (0.25, 0.5, and 1%). The same composition and concentration of aspirin nanoparticles were administered to the other three groups. The reaction time was assessed after aspirin was topically applied at 2-, 10-, 20-, 30-, 40-, 50- and 60-minute intervals. Extended delay durations in comparison to control values were used to express the ant-nociceptive effects of aspirin. The results of the study showed that aspirin nanoparticles produced the best analgesic impact, followed by the cream and then the ointment, according to the data. This suggests that the form in which aspirin is administered can significantly influence its effectiveness as an analgesic. The use of nanoparticles may increase the bioavailability of aspirin, allowing it to be more efficiently absorbed by the body and produce a more significant analgesic effect. Overall, the study's findings suggest that aspirin nanoparticles may be a more effective form of aspirin for pain relief than ordinary particles. Further research is needed to explore the potential benefits and drawbacks of this form of aspirin and determine its efficacy in human subjects. Nevertheless, the current study provides valuable insights into the factors that can influence the effectiveness of aspirin as an analgesic and may inform future developments in pain management.

THE IMPACT OF ALOE VERA GEL ON REMINERALIZATION OF THE TOOTH AND ITS EFFECT AGAINST ENTEROCOCCUS FAECALIS: AN IN VITRO STUDY

The Aloe vera plant is a cactus-like plant in the Liliacea family that has been known and utilized for its medical benefits. It has been attempted to be used as a remineralizing agent and shows an antibacterial effect. Aim of the study - assessment of the remineralizing effect of solution of saturated Aloe vera gel compared to distal water by microhardness Vickers test and Densometric X-Ray Analysis and effect of Aloe vera gel against Enterococcus faecalis. 10 extracted permanent molars were used in this in vitro study. each tooth enrolls in Teflon tape and only the enamel of the occlusal surface was exposed to a demineralizing solution (acid etch) for 45 seconds in-vitro and randomly assigned to two groups: Group 1 was treated with distal water; group 2 was treated with Aloe vera gel. All groups except the control baseline group were treated with their respective remineralizing solution for 10 days. Vicker's Microhardness Number (VHN) and Densometric X-Ray Analysis were carried out at baseline, post-demineralization and later post 10 days of remineralization. The antibacterial effect of Aloe vera gel was assessed by the disc diffusion method. The filter paper was immersed in 20µl of different concentrations of Aloe vera gel extract as fresh Aloe vera (100 %) and (50 % and 25 %) diluted with de-ionized water after that the disc was distributed in a plate containing the E. faecalis. Antibiotics disc of Augmentin (Amoxicillin and Clavulanic acid 30ug) were also poured in the same plate and incubated at 37°C for 24 hours and the zone of inhibition of antibiotic was measured for comparison with a zone of inhibition of filter paper saturated with Aloe vera gel. Densitometric X-Ray Analysis and Microhardness Number (VHN) evaluation showed improvement in the enamel density and the surface hardness after remineralization. The mean value in the group treated with Aloe vera solution was higher than the recorded mean value for the group treated with distal water. There was a significant difference between Aloe vera solution and distal water. Significant (p-value≤0.05) after 10 days. The antibacterial effect showed that E. faecalis was resistant to Aloe vera gel in different concentrations compared with Augmentin (Amoxicillin and Clavulanic acid 30ug). Aloe vera gel could be used for caries prevention in terms of safety and efficiency. While E. faecalis show resistance activity against Aloe vera gel.

A recurrent, homozygous EMC10 frameshift variant is associated with a syndrome of developmental delay with variable seizures and dysmorphic features

PURPOSE

The endoplasmic reticulum membrane complex (EMC) is a highly conserved, multifunctional 10-protein complex related to membrane protein biology. In seven families, we identified 13 individuals with highly overlapping phenotypes who harbor a single identical homozygous frameshift variant in EMC10.

METHODS

Using exome, genome, and Sanger sequencing, a recurrent frameshift EMC10 variant was identified in affected individuals in an international cohort of consanguineous families. Multiple families were independently identified and connected via Matchmaker Exchange and internal databases. We assessed the effect of the frameshift variant on EMC10 RNA and protein expression and evaluated EMC10 expression in normal human brain tissue using immunohistochemistry.

RESULTS

A homozygous variant EMC10 c.287delG (Refseq NM_206538.3, p.Gly96Alafs*9) segregated with affected individuals in each family, who exhibited a phenotypic spectrum of intellectual disability (ID) and global developmental delay (GDD), variable seizures and variable dysmorphic features (elongated face, curly hair, cubitus valgus, and arachnodactyly). The variant arose on two founder haplotypes and results in significantly reduced EMC10 RNA expression and an unstable truncated EMC10 protein.

CONCLUSION

We propose that a homozygous loss-of-function variant in EMC10 causes a novel syndromic neurodevelopmental phenotype. Remarkably, the recurrent variant is likely the result of a hypermutable site and arose on distinct founder haplotypes.

Recessive Mutations in SYNPO2 as a Candidate of Monogenic Nephrotic Syndrome

Introduction

Most of the approximately 60 genes that if mutated cause steroid-resistant nephrotic syndrome (SRNS) are highly expressed in the glomerular podocyte, rendering SRNS a “podocytopathy.”

Methods

We performed whole-exome sequencing (WES) in 1200 nephrotic syndrome (NS) patients.

Results

We discovered homozygous truncating and homozygous missense mutation in SYNPO2 (synaptopodin-2) (p.Lys1124∗ and p.Ala1134Thr) in 2 patients with childhood-onset NS. We found SYNPO2 expression in both podocytes and mesangial cells; however, notably, immunofluorescence staining of adult human and rat kidney cryosections indicated that SYNPO2 is localized mainly in mesangial cells. Subcellular localization studies reveal that in these cells SYNPO2 partially co-localizes with α-actinin and filamin A−containing F-actin filaments. Upon transfection in mesangial cells or podocytes, EGFP-SYNPO2 co-localized with α-actinin-4, which gene is mutated in autosomal dominant SRNS in humans. SYNPO2 overexpression increases mesangial cell migration rate (MMR), whereas shRNA knockdown reduces MMR. Decreased MMR was rescued by transfection of wild-type mouse Synpo2 cDNA but only partially by cDNA representing mutations from the NS patients. The increased mesangial cell migration rate (MMR) by SYNPO2 overexpression was inhibited by ARP complex inhibitor CK666. SYNPO2 shRNA knockdown in podocytes decreased active Rac1, which was rescued by transfection of wild-type SYNPO2 cDNA but not by cDNA representing any of the 2 mutant variants.

Conclusion

We show that SYNPO2 variants may lead to Rac1-ARP3 dysregulation, and may play a role in the pathogenesis of nephrotic syndrome.

Regulation of human cerebral cortical development by EXOC7 and EXOC8, components of the exocyst complex, and roles in neural progenitor cell proliferation and survival

PURPOSE

The exocyst complex is a conserved protein complex that mediates fusion of intracellular vesicles to the plasma membrane and is implicated in processes including cell polarity, cell migration, ciliogenesis, cytokinesis, autophagy, and fusion of secretory vesicles. The essential role of these genes in human genetic disorders, however, is unknown.

METHODS

We performed homozygosity mapping and exome sequencing of consanguineous families with recessively inherited brain development disorders. We modeled an EXOC7 splice variant in vitro and examined EXOC7 messenger RNA (mRNA) expression in developing mouse and human cortex. We modeled exoc7 loss-of-function in a zebrafish knockout.

RESULTS

We report variants in exocyst complex members, EXOC7 and EXOC8, in a novel disorder of cerebral cortex development. In EXOC7, we identified four independent partial loss-of-function (LOF) variants in a recessively inherited disorder characterized by brain atrophy, seizures, and developmental delay, and in severe cases, microcephaly and infantile death. In EXOC8, we found a homozygous truncating variant in a family with a similar clinical disorder. We modeled exoc7 deficiency in zebrafish and found the absence of exoc7 causes microcephaly.

CONCLUSION

Our results highlight the essential role of the exocyst pathway in normal cortical development and how its perturbation causes complex brain disorders.

PSMD12 haploinsufficiency in a neurodevelopmental disorder with autistic features

Protein homeostasis is tightly regulated by the ubiquitin proteasome pathway. Disruption of this pathway gives rise to a host of neurological disorders. Through whole exome sequencing (WES) in families with neurodevelopmental disorders, we identified mutations in PSMD12, a core component of the proteasome, underlying a neurodevelopmental disorder with intellectual disability (ID) and features of autism spectrum disorder (ASD). We performed WES on six affected siblings from a multiplex family with ID and autistic features, the affected father, and two unaffected mothers, and a trio from a simplex family with one affected child with ID and periventricular nodular heterotopia. We identified an inherited heterozygous nonsense mutation in PSMD12 (NM_002816: c.367C>T: p.R123X) in the multiplex family and a de novo nonsense mutation in the same gene (NM_002816: c.601C>T: p.R201X) in the simplex family. PSMD12 encodes a non-ATPase regulatory subunit of the 26S proteasome. We confirm the association of PSMD12 with ID, present the first cases of inherited PSMD12 mutation, and demonstrate the heterogeneity of phenotypes associated with PSMD12 mutations.

Whole-Exome Sequencing Identifies Causative Mutations in Families with Congenital Anomalies of the Kidney and Urinary Tract

BACKGROUND

Congenital anomalies of the kidney and urinary tract (CAKUT) are the most prevalent cause of kidney disease in the first three decades of life. Previous gene panel studies showed monogenic causation in up to 12% of patients with CAKUT.

METHODS

We applied whole-exome sequencing to analyze the genotypes of individuals from 232 families with CAKUT, evaluating for mutations in single genes known to cause human CAKUT and genes known to cause CAKUT in mice. In consanguineous or multiplex families, we additionally performed a search for novel monogenic causes of CAKUT.

RESULTS

In 29 families (13%), we detected a causative mutation in a known gene for isolated or syndromic CAKUT that sufficiently explained the patient's CAKUT phenotype. In three families (1%), we detected a mutation in a gene reported to cause a phenocopy of CAKUT. In 15 of 155 families with isolated CAKUT, we detected deleterious mutations in syndromic CAKUT genes. Our additional search for novel monogenic causes of CAKUT in consanguineous and multiplex families revealed a potential single, novel monogenic CAKUT gene in 19 of 232 families (8%).

CONCLUSIONS

We identified monogenic mutations in a known human CAKUT gene or CAKUT phenocopy gene as the cause of disease in 14% of the CAKUT families in this study. Whole-exome sequencing provides an etiologic diagnosis in a high fraction of patients with CAKUT and will provide a new basis for the mechanistic understanding of CAKUT.

Mutations in Human Accelerated Regions Disrupt Cognition and Social Behavior

Comparative analyses have identified genomic regions potentially involved in human evolution but do not directly assess function. Human accelerated regions (HARs) represent conserved genomic loci with elevated divergence in humans. If some HARs regulate human-specific social and behavioral traits, then mutations would likely impact cognitive and social disorders. Strikingly, rare biallelic point mutations-identified by whole-genome and targeted "HAR-ome" sequencing-showed a significant excess in individuals with ASD whose parents share common ancestry compared to familial controls, suggesting a contribution in 5% of consanguineous ASD cases. Using chromatin interaction sequencing, massively parallel reporter assays (MPRA), and transgenic mice, we identified disease-linked, biallelic HAR mutations in active enhancers for CUX1, PTBP2, GPC4, CDKL5, and other genes implicated in neural function, ASD, or both. Our data provide genetic evidence that specific HARs are essential for normal development, consistent with suggestions that their evolutionary changes may have altered social and/or cognitive behavior. PAPERCLIP.

Mutations in PYCR2, Encoding Pyrroline-5-Carboxylate Reductase 2, Cause Microcephaly and Hypomyelination

Despite recent advances in understanding the genetic bases of microcephaly, a large number of cases of microcephaly remain unexplained, suggesting that many microcephaly syndromes and associated genes have yet to be identified. Here, we report mutations in PYCR2, which encodes an enzyme in the proline biosynthesis pathway, as the cause of a unique syndrome characterized by postnatal microcephaly, hypomyelination, and reduced cerebral white-matter volume. Linkage mapping and whole-exome sequencing identified homozygous mutations (c.355C>T [p.Arg119Cys] and c.751C>T [p.Arg251Cys]) in PYCR2 in the affected individuals of two consanguineous families. A lymphoblastoid cell line from one affected individual showed a strong reduction in the amount of PYCR2. When mutant cDNAs were transfected into HEK293FT cells, both variant proteins retained normal mitochondrial localization but had lower amounts than the wild-type protein, suggesting that the variant proteins were less stable. A PYCR2-deficient HEK293FT cell line generated by genome editing with the clustered regularly interspaced short palindromic repeat (CRISPR)-Cas9 system showed that PYCR2 loss of function led to decreased mitochondrial membrane potential and increased susceptibility to apoptosis under oxidative stress. Morpholino-based knockdown of a zebrafish PYCR2 ortholog, pycr1b, recapitulated the human microcephaly phenotype, which was rescued by wild-type human PYCR2 mRNA, but not by mutant mRNAs, further supporting the pathogenicity of the identified variants. Hypomyelination and the absence of lax, wrinkly skin distinguishes this condition from that caused by previously reported mutations in the gene encoding PYCR2's isozyme, PYCR1, suggesting a unique and indispensable role for PYCR2 in the human CNS during development.

METTL23, a transcriptional partner of GABPA, is essential for human cognition

Whereas many genes associated with intellectual disability (ID) encode synaptic proteins, transcriptional defects leading to ID are less well understood. We studied a large, consanguineous pedigree of Arab origin with seven members affected with ID and mild dysmorphic features. Homozygosity mapping and linkage analysis identified a candidate region on chromosome 17 with a maximum multipoint logarithm of odds score of 6.01. Targeted high-throughput sequencing of the exons in the candidate region identified a homozygous 4-bp deletion (c.169_172delCACT) in the METTL23 (methyltransferase like 23) gene, which is predicted to result in a frameshift and premature truncation (p.His57Valfs*11). Overexpressed METTL23 protein localized to both nucleus and cytoplasm, and physically interacted with GABPA (GA-binding protein transcription factor, alpha subunit). GABP, of which GABPA is a component, is known to regulate the expression of genes such as THPO (thrombopoietin) and ATP5B (ATP synthase, H+ transporting, mitochondrial F1 complex, beta polypeptide) and is implicated in a wide variety of important cellular functions. Overexpression of METTL23 resulted in increased transcriptional activity at the THPO promoter, whereas knockdown of METTL23 with siRNA resulted in decreased expression of ATP5B, thus revealing the importance of METTL23 as a regulator of GABPA function. The METTL23 mutation highlights a new transcriptional pathway underlying human intellectual function.

Deletions in GRID2 lead to a recessive syndrome of cerebellar ataxia and tonic upgaze in humans

OBJECTIVE

To identify the genetic cause of a syndrome causing cerebellar ataxia and eye movement abnormalities.

METHODS

We identified 2 families with cerebellar ataxia, eye movement abnormalities, and global developmental delay. We performed genetic analyses including single nucleotide polymorphism genotyping, linkage analysis, array comparative genomic hybridization, quantitative PCR, and Sanger sequencing. We obtained eye movement recordings of mutant mice deficient for the ortholog of the identified candidate gene, and performed immunohistochemistry using human and mouse brain specimens.

RESULTS

All affected individuals had ataxia, eye movement abnormalities, most notably tonic upgaze, and delayed speech and cognitive development. Homozygosity mapping identified the disease locus on chromosome 4q. Within this region, a homozygous deletion of GRID2 exon 4 in the index family and compound heterozygous deletions involving GRID2 exon 2 in the second family were identified. Grid2-deficient mice showed larger spontaneous and random eye movements compared to wild-type mice. In developing mouse and human cerebella, GRID2 localized to the Purkinje cell dendritic spines. Brain MRI in 2 affected children showed progressive cerebellar atrophy, which was more severe than that of Grid2-deficient mice.

CONCLUSIONS

Biallelic deletions of GRID2 lead to a syndrome of cerebellar ataxia and tonic upgaze in humans. The phenotypic resemblance and similarity in protein expression pattern between humans and mice suggest a conserved role for GRID2 in the synapse organization between parallel fibers and Purkinje cells. However, the progressive and severe cerebellar atrophy seen in the affected individuals could indicate an evolutionarily unique role for GRID2 in the human cerebellum.

Using whole-exome sequencing to identify inherited causes of autism

Despite significant heritability of autism spectrum disorders (ASDs), their extreme genetic heterogeneity has proven challenging for gene discovery. Studies of primarily simplex families have implicated de novo copy number changes and point mutations, but are not optimally designed to identify inherited risk alleles. We apply whole-exome sequencing (WES) to ASD families enriched for inherited causes due to consanguinity and find familial ASD associated with biallelic mutations in disease genes (AMT, PEX7, SYNE1, VPS13B, PAH, and POMGNT1). At least some of these genes show biallelic mutations in nonconsanguineous families as well. These mutations are often only partially disabling or present atypically, with patients lacking diagnostic features of the Mendelian disorders with which these genes are classically associated. Our study shows the utility of WES for identifying specific genetic conditions not clinically suspected and the importance of partial loss of gene function in ASDs.

Phenotypic heterogeneity in Woodhouse-Sakati syndrome: two new families with a mutation in the C2orf37 gene

Hypogonadism, alopecia, diabetes mellitus, mental retardation, and extrapyramidal syndrome [also known as Woodhouse-Sakati syndrome (WSS)] is a rare autosomal recessive neuroendocrine and ectodermal disorder. The syndrome was first described by Woodhouse and Sakati in 1983, and 47 patients from 23 families have been reported so far. We report on an additional seven patients (four males and three females) from two highly consanguineous Arab families from Qatar, presenting with a milder phenotype of WSS. These patients show the spectrum of clinical features previously found in WSS, but lack evidence of diabetes mellitus and extrapyramidal symptoms. These two new families further illustrate the natural course and the interfamilial phenotypic variability of WSS that may lead to challenges in making the diagnosis. In addition, our study suggests that WSS may not be as infrequent in the Arab world as previously thought.

A homozygous mutation in the tight-junction protein JAM3 causes hemorrhagic destruction of the brain, subependymal calcification, and congenital cataracts

The tight junction, or zonula occludens, is a specialized cell-cell junction that regulates epithelial and endothelial permeability, and it is an essential component of the blood-brain barrier in the cerebrovascular endothelium. In addition to functioning as a diffusion barrier, tight junctions are also involved in signal transduction. In this study, we identified a homozygous mutation in the tight-junction protein gene JAM3 in a large consanguineous family from the United Arab Emirates. Some members of this family had a rare autosomal-recessive syndrome characterized by severe hemorrhagic destruction of the brain, subependymal calcification, and congenital cataracts. Their clinical presentation overlaps with some reported cases of pseudo-TORCH syndrome as well as with cases involving mutations in occludin, another component of the tight-junction complex. However, massive intracranial hemorrhage distinguishes these patients from others. Homozygosity mapping identified the disease locus in this family on chromosome 11q25 with a maximum multipoint LOD score of 6.15. Sequence analysis of genes in the candidate interval uncovered a mutation in the canonical splice-donor site of intron 5 of JAM3. RT-PCR analysis of a patient lymphoblast cell line confirmed abnormal splicing, leading to a frameshift mutation with early termination. JAM3 is known to be present in vascular endothelium, although its roles in cerebral vasculature have not been implicated. Our results suggest that JAM3 is essential for maintaining the integrity of the cerebrovascular endothelium as well as for normal lens development in humans.

Haplotype analysis of a BRCA1: 185delAG mutation in a Chilean family supports its Ashkenazi origins

At least 25% of Ashkenazi Jewish families with two or more cases of premenopausal breast cancers are attributable to one of three founder mutations in BRCA1 or BRCA2. As these three founder mutations are common in the Ashkenazi Jewish population ( approximately 2.5%) and can easily be tested for in a multiplex assay, establishing ethnicity can expedite genetic testing. It is not always possible, however, to conclusively establish ethnicity before offering testing. We report here the occurrence of a founder Ashkenazi Jewish BRCA1 mutation, 185delAG (also known as 187delAG), in a non-Jewish Chilean family with no reported Jewish ancestry. The linked haplotype present in this family was identical to that identified in the Ashkenazi Jewish population. This case report not only illustrates the problem of the definition of ethnicity but also points to the possibility of further studies of the frequency of founder Ashkenazi Jewish mutations in populations not generally considered to be of Ashkenazi Jewish origin.

Phenotype of a patient with pure partial trisomy 2p(p23-->pter)

We present the case of a 7-month-old girl with the karyotype 46,XX, der(13) t(2;13)(p23;p11.2).ish der(13)(wcp2+) de novo. Painting confirmed that the additional segment on 13p was of chromosome 2 origin, resulting in trisomy 2p23 -->2pter. The child had a prominent forehead with a flat hemangioma, depressed nasal bridge, protruding tongue, posteriorly angulated ears, esotropia with poor abduction of the right eye, bilateral severe myopia (-5.5 D), retinal hypopigmentation, foveal hypoplasia, and striking left optic nerve hypoplasia. She also had pectus excavatum, a protruding abdomen with diastasis recti, generalized hypotonia, delayed fine and gross motor development, grade II reflux on the left side, and grade III-IV reflux on the right side. An EEG showed epileptiform discharges. Computed tomographic scan of the brain showed decreased white matter, but magnetic resonance imaging showed normal results.

Insulin binding substances, autoimmunity and type I diabetes in Kuwaiti patients and their kindred

Insulin autoantibodies (IAAs) are associated with type I diabetes mellitus (DM) and have been suggested as predictive markers of the disease. Using an ELISA assay, we have studied the prevalence of binding to human insulin in sera from an Arab type I DM population and compared it with the prevalence in the family members (FMs) of the probands, in type II DM patients from the same population, and in Arab control subjects. Significant levels of binding occurred in 11/16 (69%) of type I DM patients and in 21/34 (62%) of their FMs, but in only 5/31 (16%) of type II DM patients and in 1/25 (4%) of control subjects. Within families, there was homogeneity with regard to the level of insulin binding and the mean family levels correlated with those of the proband (r = 0.68, df = 7, p = 0.05). HLA-DR3 or -DR4 antigens occurred in 55/63 (87%) of type I DM patients and in 95/118 (81%) of their FMs. This was significantly higher (p less than 0.001) than in either type II DM patients (39/75, 52%) or in control subjects (34/93, 37%). ICAs were present in significantly more (25/43, 58%) of type I DM patients than their FMs (3/82, 3%) (p less than 0.001). They did not occur in either type II DM patients or in the control group. In conclusion, insulin binding occurred in sera from both type I diabetic patients and their kindred, and hence did not appear to be specifically associated with the development of clinical diabetes.

HLA associations in an Arab type 1 diabetic population

We have studied HLA-A, -B, -C, -DR, and -DQ antigen frequencies in 63 Type 1 diabetic Arab patients resident in Kuwait. Both HLA-DR3 (relative risk (RR) = 5.80) and -DR4 (RR = 2.87) showed positive associations with Type I diabetes mellitus in these patients whilst -DR2 (RR 0.16) and -DR5 (RR = 0.15) were negatively associated. The strong positive association with both HLA-DR3 and -DR4 was confirmed in Non-Gulf Arabs (RR = 12.55 and 4.29, respectively) whereas the Gulf Arabs had a significant positive association with HLA-DR3 (RR = 4.41) only. The disease was negatively associated with HLA-DR2 (RR = 0.05) in Gulf Arab patients only and with HLA-DR5 (RR = 0.10) in Non-Gulf Arabs only. HLA-DRw52 and -DRw53 were increased in Non-Gulf Arabs only (RR = 3.14 and 4.63, respectively). In both groups there was strong association with HLA-DQ3 (Gulf, RR = 28.11; Non-Gulf, RR = 6.25). Amongst HLA-A, -B, and -C loci, there was a positive association with HLA-B8 (RR = 19.06).

Association between HLA-D region epitopes and multiple sclerosis in Arabs

We have studied the HLA associations of MS patients in Arab patients from two regions. Those patients from the Mediterranean area showed an association of MS with HLA-DR2 (p less than 0.001) and -DQw1 (p less than 0.05), whilst in those from the Gulf there was an association with -DRw53 (p less than 0.02). In the Mediterranean patients -DRw52 was negatively associated with MS (p less than 0.05). In the control populations from the two regions there was a considerable variation in the incidence of HLA antigens. Thus, Gulf Arabs had an increased incidence of -DR1 (p less than 0.05), -DR2 (p less than 0.02), -DR6 (p less than 0.05) and decreased incidence of -DR5 (p less than 0.05), -DRw52 (p less than 0.02) and -DQw3 (p less than 0.01) compared to the Mediterranean control population. These findings are discussed in relation to the aetiology of the disease.