Mutations in SLC19A2 cause thiamine-responsive megaloblastic anaemia associated with diabetes mellitus and deafness.

Thiamine-responsive megaloblastic anaemia (TRMA), also known as Rogers syndrome, is an early onset, autosomal recessive disorder defined by the occurrence of megaloblastic anaemia, diabetes mellitus and sensorineural deafness, responding in varying degrees to thiamine treatment (MIM 249270). We have previously narrowed the TRMA locus from a 16-cM to a 4-cM interval on chromosomal region 1q23.3 (refs 3,4) and this region has been further refined to a 1.4-cM interval. Previous studies have suggested that deficiency in a high-affinity thiamine transporter may cause this disorder. Here we identify the TRMA gene by positional cloning. We assembled a P1-derived artificial chromosome (PAC) contig spanning the TRMA candidate region. This clarified the order of genetic markers across the TRMA locus, provided 9 new polymorphic markers and narrowed the locus to an approximately 400-kb region. Mutations in a new gene, SLC19A2, encoding a putative transmembrane protein homologous to the reduced folate carrier proteins, were found in all affected individuals in six TRMA families, suggesting that a defective thiamine transporter protein (THTR-1) may underlie the TRMA syndrome.

Hypotrichosis with juvenile macular dystrophy is caused by a mutation in CDH3, encoding P-cadherin.

Congenital hypotrichosis associated with juvenile macular dystrophy (HJMD; MIM601553) is an autosomal recessive disorder of unknown etiology, characterized by hair loss heralding progressive macular degeneration and early blindness. We used homozygosity mapping in four consanguineous families to localize the gene defective in HJMD to 16q22.1. This region contains CDH3, encoding P-cadherin, which is expressed in the retinal pigment epithelium and hair follicles. Mutation analysis shows in all families a common homozygous deletion in exon 8 of CDH3. These results establish the molecular etiology of HJMD and implicate for the first time a cadherin molecule in the pathogenesis of a human hair and retinal disorder.

The deoxyguanosine kinase gene is mutated in individuals with depleted hepatocerebral mitochondrial DNA.

Mitochondrial DNA (mtDNA)-depletion syndromes (MDS; OMIM 251880) are phenotypically heterogeneous, autosomal-recessive disorders characterized by tissue-specific reduction in mtDNA copy number. Affected individuals with the hepatocerebral form of MDS have early progressive liver failure and neurological abnormalities, hypoglycemia and increased lactate in body fluids. Affected tissues show both decreased activity of the mtDNA-encoded respiratory chain complexes (I, III, IV, V) and mtDNA depletion. We used homozygosity mapping in three kindreds of Druze origin to map the gene causing hepatocerebral MDS to a region of 6.1 cM on chromosome 2p13, between markers D2S291 and D2S2116. This interval encompasses the gene (DGUOK) encoding the mitochondrial deoxyguanosine kinase (dGK). We identified a single-nucleotide deletion (204delA) within the coding region of DGUOK that segregates with the disease in the three kindreds studied. Western-blot analysis did not detect dGK protein in the liver of affected individuals. The main supply of deoxyribonucleotides (dNTPs) for mtDNA synthesis comes from the salvage pathway initiated by dGK and thymidine kinase-2 (TK2). The association of mtDNA depletion with mutated DGUOK suggests that the salvage-pathway enzymes are involved in the maintenance of balanced mitochondrial dNTP pools.

Atrichia with papular lesions resulting from a nonsense mutation within the human hairless gene.

Atrichia with papular lesions is a rare autosomal recessive form of alopecia characterized by hair loss soon after birth and the development during childhood of a diffuse papular rash. We have previously shown that this disorder results from a deleterious mutation in the human hairless gene, a gene also involved in the pathogenesis of a related but clinically distinct form of congenital alopecia, termed alopecia universalis congenita. In this report, we describe a novel nonsense mutation in exon 4 of the human hairless gene in a consanguineous kindred affected with atrichia with papular lesions. This report provides additional evidence for phenotypic heterogeneity among inherited atrichias and for an association between the papular rash of atrichia with papular lesions and nonsense mutations in the human hairless gene.

Salivary flow-rate and composition in schizophrenic patients on clozapine: subjective reports and laboratory data.

The extent of hypersalivation was evaluated in a group of 25 schizophrenic patients on clozapine. A high prevalence of the complaint was detected by a questionnaire; up to 80% of the patients complained of hypersalivation at night. Salivary flow-rate and composition was examined in 17 patients who agreed to participate and in a matched group of healthy controls. No significant differences were detected in composition or flow-rates of resting and stimulated saliva. The salivary flow-rates in the schizophrenic patients on clozapine did not correlate with the subjective complaint of hypersalivation. Because the severity and prevalence of the complaint was higher at night, a possibility of an altered circadian rhythm of salivation might be suggested in these patients.

Oral side effects of head and neck irradiation: correlation between clinical manifestations and laboratory data.

Salivary flow rate and composition, oral microflora and clinical manifestations of radiation damage were studied in 32 patients treated with external irradiation to head and neck areas. Several parameters were investigated: field arrangement, amount of salivary glands irradiated, clinical manifestations such as dryness of the mouth, taste impairment, dysphagia, salivary secretion and composition, and oral yeast flora. The salivary glands have a greater sensitivity to radiation damage than the gustatory tissues. The decrease in salivary secretion is accompanied by a rise in salivary sodium concentration, and in oral yeast flora. The clinical symptomatology was correlated with the amount of salivary glands irradiated. We found that most of the parotids have to be outside of the treated volume, when the rest of the major salivary glands are irradiated, to prevent severe dryness phenomena.

Atrichia with papular lesions maps to 8p in the region containing the human hairless gene.

Atrichia with papular lesions (APL) (OMIM 209500) is a hereditary form of alopecia. Hair loss occurs soon after birth and is followed years later by the development of a diffuse papular eruption. Its mode of transmission is still uncertain. A related but clinically distinct form of alopecia, known as alopecia universalis (OMIM 203655), has recently been found to be associated with a mutation in the human hairless gene. The present report describes the largest consanguineous kindred of APL reported to date and provides strong evidence for autosomal recessive inheritance of this rare disorder. On the basis of a linkage analysis of this kindred using six microsatellite markers spanning the human hairless gene region, we found that the APL locus maps to chromosome region 8p12 in a 5 cM interval between marker D8S560 and marker D8S1739. A maximum lodscore of 3.7 was obtained with marker D8S1786, at a recombination fraction of 0. Our results suggest phenotypic variability at the hairless locus although they do not rule out the existence of a gene cluster associated with hair disorders in the same region.

Effect of transdermal scopolamine on salivation.

The effect of transdermal scopolamine on salivary flow and composition was analyzed in 21 healthy volunteers. The flow rate of whole saliva was significantly lowered by transdermal scopolamine. Significant positive correlations were found between the placebo rate of flow and both the quantity and percentage decreases in response to transdermal scopolamine. The magnesium concentration was significantly increased during transdermal scopolamine administration, whereas the sodium, potassium, and calcium concentrations were not consistently altered. Accordingly, the magnesium secretion rate was unaltered, whereas sodium, potassium, and calcium secretion rates were significantly lowered by transdermal scopolamine administration.

Salivary and lacrimal secretions in patients on lithium therapy.

Salivary and lacrimal secretion rates and salivary composition were examined in 22 manic-depressive patients on lithium therapy and in 21 matched, healthy controls. Serum immunoglobulins (IgG and IgA) were measured in these patients. Their oral health was examined and found to be unimpaired. Significantly lowered tear secretion was detected in the patients, while their salivary secretion rates were normal. The salivary concentrations of NA, K and IgA were significantly elevated in whole saliva. In parotid saliva, the concentrations of K and IgA were elevated, while Na was in the normal range. A significant correlation between serum and salivary lithium concentrations was found, indicating the usefulness of salivary measurements for monitoring. Informed consent of the patients was obtained after the nature of the procedures had been fully explained.

Whole-saliva secretion rates in old and young healthy subjects.

Resting and stimulated whole-saliva secretion rates were compared in old and young healthy volunteers. The stimulated secretion rate was similar in both age groups, while the resting flow rate was significantly lower in the old females and males as compared with rates in the young.

Effect of exercise on salivary composition and cortisol in serum and saliva in man.

The effect of exercise on electrolytes and cortisol levels in serum and saliva was examined in 27 young, healthy male volunteers who performed graded submaximal cycle exercise for nine min at up to 85% of their age-predicted maximal heart rate. Seventeen men performed the Wingate anaerobic test for 30 s. A significant increase in pulse rate and systolic blood pressure and a decrease in diastolic blood pressure were found, and serum concentrations of Na+, K+, and lactate were significantly elevated immediately after exercise. A nonsignificant increase in saliva and serum cortisol levels was found. Significantly lowered salivary flow rate and elevated salivary K+, protein, and lactate concentrations were found within ten min after exercise. Salivary Mg2+ was significantly elevated after anaerobic exercise only.

Oral health and salivary composition in diabetic patients.

The salivary composition and flow rate were examined in 20 patients with insulin-dependent diabetes mellitus (IDDM) and in 19 patients with non-insulin-dependent diabetes mellitus (NIDDM) and compared with 20 healthy controls. Resting and stimulated whole and submandibular saliva was analyzed. Significantly lower resting salivary flow rates were found in the IDDM patients as compared to the NIDDM group. In the IDDM patients potassium concentration in resting saliva was significantly higher compared with healthy controls and in stimulated whole saliva compared with NIDDM patients. No difference in salivary total protein, amylase, lactoferrin, or lysozyme was found among the three groups examined. The IgA concentration of the IDDM patients was significantly higher in whole resting saliva compared with controls and in the submandibular saliva compared with both NIDDM patients and controls. No difference was found between controls and the diabetic patients examined in prevalence of complaint of dry mouth. The salivary flow rates, however, were significantly lower in the three subgroups with dry mouth compared with the subgroups without this complaint. Caries were detected in 100% of the diabetic patients and controls. No correlation was observed between the incidence of caries and any of the salivary parameters examined. A higher prevalence and severity of periodontal disease was detected in the diabetic patients as compared to the controls. A significant positive correlation was found between the gingival index and the concentrations of total protein, albumin, lysozyme, and lactoferrin in whole resting saliva in the three groups examined.

Composition of whole unstimulated saliva of healthy children: changes with age.

Whole unstimulated saliva was collected from 136 healthy subjects divided into 5 groups according to age: (1) 25 infants, 7-11 months old; (2) 28 toddlers, 2-3 yr old; (3) 28 children, 6-8 yr old; (4) 28 adolescents, 12-14 yr old; (5) 27 adults, 25-63 yr old. The concentrations of Na, K, total protein, IgA and amylase activity were measured. A significant ascending linear correlation with age was found for concentrations of Na, total protein, IgA and amylase activity. There were significant differences between age groups in K and IgA concentrations. Salivary amylase activity was very variable, and a significant difference was found between infants and toddlers only. Salivary composition thus changes significantly during childhood, implying a process of development and maturation of the salivary glands and indicating the need of age-matched controls for the clinical use of saliva.

Composition of whole unstimulated saliva of human infants.

Whole unstimulated saliva of 168 infants aged 3 days to 12 months was analysed. The concentration of Ca, Mg and Cl was higher in the saliva of infants than in adults. The concentration of phosphate, IgA, amylase and pH was lower in infants; Na, K and total protein did not differ significantly. A wide range of all the concentrations was observed in the saliva of infants. No significant difference was found between the salivary composition of male versus female or of breast-fed as compared to bottle-fed infants. No difference before and after eruption of teeth was detected. Significant differences between different age groups were observed in the concentrations of Na, K, Cl, phosphate, protein, amylase and pH. No significant differences were found in Ca, Mg and IgA concentrations within the first year. A negative correlation between the age of the infants and the concentrations of Na, K, Cl and total protein was observed. A positive correlation was found for phosphate and amylase as a function of age.

The concentration of salivary IgA in whole and parotid saliva and the effect of stimulation.

The concentration of salivary IgA was measured in 24 healthy volunteers. The resting salivary IgA (n = 19) was 14.5 +/- 7.5 mg/dl in parotid saliva and 6.5 +/- 3.6 mg/dl in whole saliva. After stimulation (n = 5), parotid IgA decreased to 6.8 +/- 5.0 mg/dl and whole-saliva IgA to 3.1 +/- 2.22 mg/dl. Freezing caused a diversified decrease in IgA concentration.

Salivary secretion and seasickness susceptibility.

The salivary flow rate and composition of 2 groups of 31 subjects, one group at each extreme of the seasickness susceptibility scale, were compared. No significant differences were found between the two groups in flow rates and electrolyte concentrations of whole resting and stimulated saliva. Amylase activity and rate of secretion in resting saliva were significantly higher in subjects susceptible to seasickness as compared with nonsusceptible subjects. Also, the total protein rate of secretion in resting saliva was significantly higher in the susceptible group. The present findings could be explained in terms of higher sympathetic tone in subjects susceptible to seasickness, and salivary amylase levels might be recommended as an additional parameter in the evaluation of seasickness susceptibility.

Synphilin-1 isoforms in Parkinson's disease: regulation by phosphorylation and ubiquitylation.

Parkinson's disease (PD) is characterized by the death of dopaminergic neurons and the presence of Lewy bodies in the substantia nigra pars compacta. The mechanisms involved in the death of neurons as well as the role of Lewy bodies in the pathogenesis of the disease are still unclear. Lewy bodies are made of aggregated proteins, in which alpha-synuclein represents their major component. Alpha-synuclein interacts with synphilin-1, a protein that is also present in Lewy bodies. When expressed in cells, synphilin-1 forms inclusions together with alpha-synuclein that resemble Lewy bodies. Synphilin-1 is ubiquitylated by various E3 ubiquitin-ligases, such as SIAH, parkin and dorfin. Ubiquitylation of synphilin-1 by SIAH is essential for its aggregation into inclusions. We recently identified a new synphilin-1 isoform, synphilin-1A, that is toxic to neurons, aggregation-prone and accumulates in detergent-insoluble fractions of brains from alpha-synucleinopathy patients. Synphilin-1A inclusions recruit both alpha-synuclein and synphilin-1. Aggregation of synphilin-1 and synphilin-1A seems to be protective to cells. We now discuss several aspects of the neurobiology and pathology of synphilin-1 isoforms, focusing on possible implications for PD.

Defective deoxyribonucleic acid replication of T4rII bacteriophage in lambda-lysogenic host cells.

Sedimentation of the replicative deoxyribonucleic acid through alkaline sucrose gradients showed that rII single chains reached the half-mature size at a time when wild-type molecules formed long chains (dimers and trimers of genome size). Long rII single chains could be observed on substitution of tris(hydroxymethyl)aminomethane buffer for Na(+)K(+) phosphate in the growth medium.