Exon and intron sequences, respectively, repress and activate splicing of a fibroblast growth factor receptor 2 alternative exon.

Two alternative exons, BEK and K-SAM, code for part of the ligand binding site of fibroblast growth factor receptor 2. Splicing of these exons is mutually exclusive, and the choice between them is made in a tissue-specific manner. We identify here pre-mRNA sequences involved in controlling splicing of the K-SAM exon. The short K-SAM exon sequence 5'-TAGGGCAGGC-3' inhibits splicing of the exon. This inhibition can be overcome by mutating either the exon's 5' or 3' splice site to make it correspond more closely to the relevant consensus sequence. Two separate sequence elements in the intron immediately downstream of the K-SAM exon, one of which is a sequence rich in pyrimidines, are both needed for efficient K-SAM exon splicing. This is no longer the case if either the exon's 5' or 3' splice site is reinforced. Furthermore, if the exon inhibitory sequence is removed, the intron sequences are not required for splicing of the K-SAM exon in a cell line which normally splices this exon. At least three elements are thus involved in controlling splicing of the K-SAM exon: suboptimal 5' and 3' splice sites, an exon inhibitory sequence, and intron activating sequences.

Control of BEK and K-SAM splice sites in alternative splicing of the fibroblast growth factor receptor 2 pre-mRNA.

The fibroblast growth factor receptor 2 gene pre-mRNA can be spliced by using either the K-SAM exon or the BEK exon. The exon chosen has a profound influence on the ligand-binding specificity of the receptor obtained. Cells make a choice between the two alternative exons by controlling use of both exons. Using fibroblast growth factor receptor 2 minigenes, we have shown that in cells normally using the K-SAM exon, the BEK exon is not used efficiently even in the absence of the K-SAM exon. This is because these cells apparently express a titratable repressor of BEK exon use. In cells normally using the BEK exon, the K-SAM exon is not used efficiently even in the absence of a functional BEK exon. Three purines in the K-SAM polypyrimidine tract are at least in part responsible for this, as their mutation to pyrimidines leads to efficient use of the K-SAM exon, while mutating the BEK polypyrimidine tract to include these purines stops BEK exon use.

Multiple interdependent sequence elements control splicing of a fibroblast growth factor receptor 2 alternative exon.

The fibroblast growth factor receptor 2 gene contains a pair of mutually exclusive alternative exons, one of which (K-SAM) is spliced specifically in epithelial cells. We have described previously (F. Del Gatto and R. Breathnach, Mol. Cell. Biol. 15:4825-4834, 1995) some elements controlling K-SAM exon splicing, namely weak exon splice sites, an exon-repressing sequence, and an intron-activating sequence. We identify here two additional sequences in the intron downstream from the K-SAM exon which activate splicing of the exon. The first sequence (intron-activating sequence 2 [IAS2]) lies 168 to 186 nucleotides downstream from the exon's 5' splice site. The second sequence (intron-activating sequence 3 [IAS3]) lies 933 to 1,052 nucleotides downstream from the exon's 5' splice site. IAS3 is a complex region composed of several parts, one of which (nucleotides 963 to 983) can potentially form an RNA secondary structure with IAS2. This structure is composed of two stems separated by an asymmetric bulge. Mutations which disrupt either stem decrease activation, while compensatory mutations which reestablish the stem restore activation, either completely or partially, depending on the mutation. We present a model for K-SAM exon splicing involving the intervention of multiple, interdependent pre-mRNA sequence elements.

Structure of the promoter for the human macrophage stimulating protein receptor gene.

The macrophage stimulating protein receptor is a receptor protein tyrosine kinase of the met/hepatocyte growth factor receptor family. Binding of the macrophage stimulating protein to its receptor provokes changes in cell morphology and motility. Here we report the structure of the promoter of the gene coding for this receptor. The major transcription start sites have been identified. The 5' flanking region has characteristics of other receptor tyrosine kinase gene promoters, namely several GC boxes but the absence of a TATA box. Deletion analysis shows that multiple elements are needed for full promoter activity.

Study of the P300 and cerebral maps in subjects with multi-infarct dementia treated with cytidine.

A study of event-related P300 potential and cerebral EEG maps was performed in 20 patients affected by multi-infarct dementia (MID): 10 subjects were treated with placebo and 10 with cytidine. The trial was divided into three intervals. The patients, after a period of washout, were evaluated throughout the course of the trial by electrophysiological examination performed at baseline, after 90 min from the first IV injection, again after 30 days of IM therapy, and finally after 60 days of continued IM therapy. In the group treated with cytidine, the findings relevant to the study of the P300 showed a significant decrease in latency values compared to baseline (P less than 0.05 ANOVA) and an improvement. though not significant, in the amplitude values. Calculation of the mean relative power of EEG values showed a significant decrease in delta activity and an increase in alpha activity. In the subjects treated with placebo, no statistically significant variation was found in either P300 or EEG map recordings. On the basis of these investigations it has been demonstrated that the variations in the registrations can be correlated to the improved neuronal activity following treatment with cytidine.

Age correlation in the bulbo-cavernosus reflex.

A study was conducted in 120 normal male subjects (age range 15-20 years) by testing the bulbo-cavernosus reflex (BCR). The mean latency +/- SD of the reflex was 32.9 +/- 0.7 ms. BCR latency values reported in subjects grouped according to age (15-20, 21-30, 31-40, 41-50, 51-60, 61-70) did not vary significantly for individuals between the ages of 15 and 50; whereas, the latency values for the older age groups (5th and 6th groups), were statistically significant. In conclusion, the authors attribute the increased latency associated with age to changes which occur in the fibres of the nerve pathways and emphasize the importance of collecting normative data according to age groups.

The exon sequence TAGG can inhibit splicing.

The fibroblast growth factor receptor-2 gene contains a pair of alternative exons, K-SAM and BEK, which are spliced in a cell type specific manner. We have shown previously that a 10 nucleotide sequence within the K-SAM exon exerts a negative effect on K-SAM exon splicing independent of cell type. We demonstrate here that this sequence works autonomously, as it can repress splicing of a heterologous exon, the EIIIb alternative exon of the rat fibronectin gene. By introducing point mutations into the 10 nucleotide sequence, we have shown that the functional portion is limited to 4 nucleotides, TAGG, the dinucleotide AG of which is particularly important. This short sequence may participate in the control of splicing of exons carrying it, provided that they carry weak splice sites.

Somatosensory-evoked potential study in headache patients.

Somatosensory-evoked potentials (SEPs) after median nerve stimulation were studied in 34 patients with common migraine, in 30 patients with muscle-contraction headache, and in 10 cluster headache patients. The SEPs were registered before and after histamine administration. Latency values in common migraineurs showed no variation when compared with those in controls. Although not statistically significant, the N1-P2 amplitude was increased in 14 (41.1%) of these patients after histamine stimulation. No changes were observed in muscle-contraction headache patients either with or without histamine administration. In all cluster headache patients, the N1-P2 amplitude decreased after histamine stimulation. These results are discussed in the light of current hypotheses concerning the pathophysiologic mechanisms of headache.

Neuropathy in children and adolescents with diabetes mellitus.

Nerve conduction velocities were studied in the median, posterior tibial, radial and sural nerves of 50 juvenile diabetics, average age 13 +/- 1.3 years and mean duration of diabetes 2.3 +/- 1.4 years. Motor conduction velocity (MCV) in the median nerve was reduced in 10% of the subjects, and in the posterior tibial in 32%. Sensory conduction velocity (SCV) in the radial nerve was reduced in 30% of the subjects, and in the sural in 44%. No relationship was found between the reduction in conduction velocity and the duration of diabetes; nevertheless, a correlation was observed between this reduction and the degree of glycaemic control represented by the glycosylated haemoglobin concentration. The authors emphasize the importance of good glycaemic control for the prevention of diabetic neuropathy.

Effects of uridine in the treatment of diabetic neuropathy: an electrophysiological study.

The authors performed a controlled double-blind neurophysiological study (uridine vs placebo) in 40 diabetic patients with peripheral neuropathy. Twenty subjects were treated with uridine and 20 with placebo. The neurophysiological evaluation consisted of a study of the MCV of the median nerve, the common Peroneal, the posterior Tibial, the SCV of the radial nerve, the median and the sural as well as the amplitudes of the motor and sensory responses. The nerves examined were on the dominant side. The evaluations were performed at baseline and after 60, 120, 180 days of therapy with a follow up control after 90 days from the completion of therapy. No statistically significant modifications were observed in the placebo group. In the drug group, the neurophysiological parameters improved significantly from the 120th day post therapy compared with baseline and were maintained through to follow up. The authors discuss the results which demonstrated that treatment with uridine can bring about a neurophysiological improvement in peripheral nerves.

A clinical and neurophysiological trial on nootropic drugs in patients with mental decline.

The different expressions of mental decline in elderly people, from simple senile benign forgetfulness to SDAT, can be evaluated by psychometric and neurophysiological tests. In the present study, the effects of oxiracetam, piracetam and placebo were compared in a group of elderly subjects. The results of the trial, structured as single blind, clearly showed that nootropics positively effect both clinical and neurophysiological performances and that oxiracetam produces a more pronounced effect when compared to piracetam. In fact, oxiracetam was found more effective in improving psychometric scales such as GDS (clinical performances) as well as the amplitude and the latency of the P300 (neurophysiological performances), which reflect a functional recovery of the cerebral pathways related to attention and memory.