[Not a pneumothorax again! Birt-Hogg-Dubé syndrome: a case report]

Case discussion of a 40-year-old male patient with a history of recurrent pneumothoraces due to Birt-Hogg-Dubé syndrome. In addition to conservative treatment of a pneumothorax on the left side, a subtotal parietal pleurectomy on the right side was performed after recurrence of a pneumothorax 6 years later. CT of the thorax showed high-grade structural remodelling of the lung parenchyma with cystic lung lesions on both sides with a diameter of up to 7.5 cm. After exclusion of alpha-1 antitrypsin deficiency, underlying immunological disease, unremarkable family and occupational history, Birt-Hogg-Dubé syndrome was suspected based on the morphological distribution pattern of the cystic lung lesions. Genetic examination helped detect a heterozygous pathogenic variant in the FLCN gene, namely c.1294_1298del;p.(Ser432Argfs*22). Birt-Hogg-Dubé syndrome is a rare genetic disorder clinically characterized by pulmonary cysts, fibrofolliculomas of the skin and occurrence of clustered renal tumors. In particular, the increased risk of renal malignancies and the risk of spontaneous pneumothoraces underlines the importance of early diagnosis and screening of affected patients and their families.

Fluorescent annulated imidazo[4,5-c]isoquinolines via a GBB-3CR/imidoylation sequence - DNA-interactions in pUC-19 gel electrophoresis mobility shift assay

Herein we report the development of a sequential synthesis route towards annulated imidazo[4,5-c]isoquinolines comprising a GBB-3CR, followed by an intramolecular imidoylative cyclisation. X-Ray crystallography revealed a flat 3D structure of the obtained polyheterocycles. Thus, we evaluated their interactions with double-stranded DNA by establishing a pUC-19 plasmid-based gel electrophoresis mobility shift assay, revealing a stabilising effect on ds-DNA against strand-break inducing conditions.

Remarkable effect of transdermal nicotine in children with CHRNA4-related autosomal dominant sleep-related hypermotor epilepsy

OBJECTIVE

Autosomal dominant sleep-related hypermotor epilepsy (ADSHE) is characterized by hypermotor seizures and may be caused by gain-of-function mutations affecting the nicotinic acetylcholine receptor (nAChR). Benefit from nicotine consumption has been reported in adult patients with this disorder. For the first time, the effect of transdermal nicotine is evaluated in children.

METHODS

Transdermal nicotine was applied to three boys, two aged 10 years (7 mg/24 h) and one six years (3.5 mg/24 h). Autosomal dominant sleep-related hypermotor epilepsy was caused by the p.S280F-CHRNA4 (cholinergic receptor, nicotinic, alpha polypeptide 4) mutation. The children suffered from frequent, persistent nocturnal seizures and had developed educational and psychosocial problems. Seizure frequency and cognitive and behavioral parameters were assessed before and after treatment.

RESULTS

A striking seizure reduction was reported soon after treatment onset. Hypermotor seizures disappeared; only sporadic arousals, sometimes with minor motor elements, were observed. Psychometric testing documented improvement in cognitive domains such as visuospatial ability, processing speed, memory, and some areas of executive functions.

SIGNIFICANCE

Nicotine appears to be a mechanistic treatment for this specific disorder, probably because of desensitization of the mutated receptors. It may control seizures resistant to conventional drugs for epilepsy and impact socioeducational function in children. This mode of precision therapy should receive more attention and should be available to more patients with uncontrolled CHRNA4-related ADSHE across the age span.

Glucocorticoid receptor overexpression slightly shifts microRNA expression patterns in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a particularly aggressive subtype of breast cancer with limited options for clinical intervention. As with many solid tumors, TNBC is known to promote invasiveness and metastasis by secreting extracellular vesicles (EVs) capable of modulating the behaviour of recipient cells. Recent investigations have demonstrated that high expression levels of glucocorticoid receptor (GR) in TNBC are linked to therapy resistance, higher recurrence rates and increased mortality. In addition to activating protein-coding genes, GR is also involved in the expression of short non-coding RNAs including microRNAs (miRNAs or miRs). The molecular mechanisms responsible for the oncogenic effects of GR on TNBC have yet to be fully elucidated; however, emerging evidence suggests that miRNAs may play a pivotal role in tumorigenesis and metastasis. Thus, the aim of this study was to identify GR-regulated cellular and vesicular miRNAs that might contribute to the particularly oncogenic phenotype of TNBC with a high GR expression. We analyzed miRNA profiles of three TNBC cell lines using an in vitro model of GR overexpression. Next-generation sequencing revealed minor, cell line-specific changes in cellular miRNA expression, whereas vesicular miRNAs were not significantly regulated by GR. Additionally, the analysis of predicted miRNA targets failed to establish a causal link between GR-induced miRNA expression and oncogenic signaling. On the whole, given that GR influences miRNA profiles to only a small degree, other mechanisms are more likely to be responsible for the increased mortality of patients with TNBC with a high GR expression.

A fluorescence in situ hybridization-based screen allows rapid detection of adverse cytogenetic alterations in patients with acute myeloid leukemia

In adult acute myeloid leukemia (AML), the karyotype of the leukemic cell is among the strongest prognostic factors. The Medical Research Council (MRC) and the European LeukemiaNet (ELN) classifications distinguish between favorable, intermediate and adverse cytogenetic risk patients who differ in their treatment response and overall survival. Conventional cytogenetic analyses are a mandatory component of AML diagnostics but they are time-consuming; therefore, therapeutic decisions in elderly patients are often delayed. We investigated whether a screening approach using a panel of seven fluorescence in situ hybridization (FISH) probes would allow rapid identification of adverse chromosomal changes. In a cohort of 334 AML patients, our targeted FISH screening approach identified 80% of adverse risk AML patients with a specificity of 99%. Incorporating FISH screening into diagnostic workup has the potential to accelerate risk stratification and treatment selection, particularly in older patients. This approach may allow therapeutic decisions more quickly, which benefits both patients and physicians and might save costs.

Association of Common Polymorphisms in the Nicotinic Acetylcholine Receptor Alpha4 Subunit Gene with an Electrophysiological Endophenotype in a Large Population-Based Sample

Variation in genes coding for nicotinic acetylcholine receptor (nAChR) subunits affect cognitive processes and may contribute to the genetic architecture of neuropsychiatric disorders. Single nucleotide polymorphisms (SNPs) in the CHRNA4 gene that codes for the alpha4 subunit of alpha4/beta2-containing receptors have previously been implicated in aspects of (mostly visual) attention and smoking-related behavioral measures. Here we investigated the effects of six synonymous but functional CHRNA4 exon 5 SNPs on the N100 event-related potential (ERP), an electrophysiological endophenotype elicited by a standard auditory oddball. A total of N = 1,705 subjects randomly selected from the general population were studied with electroencephalography (EEG) as part of the German Multicenter Study on nicotine addiction. Two of the six variants, rs1044396 and neighboring rs1044397, were significantly associated with N100 amplitude. This effect was pronounced in females where we also observed an effect on reaction time. Sequencing of the complete exon 5 region in the population sample excluded the existence of additional/functional variants that may be responsible for the observed effects. This is the first large-scale population-based study investigation the effects of CHRNA4 SNPs on brain activity measures related to stimulus processing and attention. Our results provide further evidence that common synonymous CHRNA4 exon 5 SNPs affect cognitive processes and suggest that they also play a role in the auditory system. As N100 amplitude reduction is considered a schizophrenia-related endophenotype the SNPs studied here may also be associated with schizophrenia outcome measures.

Increased chromosome 16 disomy rates in human spermatozoa and recurrent spontaneous abortions

OBJECTIVE

To investigate if unexplained recurrent spontaneous abortions (RSA) are associated with increased rates of aneuploidy in spermatozoa of RSA partners ("RSA-men").

DESIGN

Case-control study.

SETTING

Academic research center.

PATIENT(S)

Patients enrolled at the Hormone and Fertility Center and controls at the Department of Urology (LMU-Munich).

INTERVENTION(S)

Sperm samples of 11 partners of unexplained RSA cases evaluated for elevated diploidy and disomy levels of chromosomes 1-22, X, and Y by multicolor sperm fluorescence in situ hybridization (FISH).

MAIN OUTCOME MEASURE(S)

Aneuploidy rates obtained in RSA-men compared with controls from the literature and internally; an increase of the aneuploidy rate was considered statistically significant, when it differed ≥ 2 standard deviations from the mean baseline level in controls.

RESULT(S)

Our sperm FISH data on RSA men showed increased disomy rates for at least three chromosomes in more than 60% of patients but no statistically significant increase of the overall mean sperm disomy or diploidy rate. In particular, meiotic errors involving chromosome 16 contributed to increased sperm disomy in more than 60% of our patients.

CONCLUSION(S)

These data suggest that among paternal meiotic errors nondisjunction of chromosome 16 might have similar relative influence on fetal aneuploidy compared with maternal chromosome 16 disomy.

2q37.3 Deletion Syndrome: Two Cases with Highly Distinctive Facial Phenotype, Discordant Association with Schizophrenic Psychosis, and Shared Deletion Breakpoint Region on 2q37.3

2q37.3 deletion syndrome belongs to the chromosomal 2q37 deletion spectrum which clinically resembles Albright hereditary osteodystrophy (AHO) syndrome. It is is mainly characterized by short stature, obesity, round face, brachydactyly type E, intellectual disability, behavioral problems, and variable intellectual deficits. Different from classical AHO syndrome, patients with 2q37 deletion syndrome lack renal parathyroid hormone resistance (pseudohypoparathyroidism) and soft tissue ossification. So far, deletion mapping or molecular breakpoint analyses of 2q37 have been performed in only few patients. Here, we report on 2 patients with 2q37.3 deletion syndrome. In both patients the breakpoint of the 5.5-Mb terminal microdeletion could be narrowed down to the same ∼ 200-kb interval on 2q37.3 by BAC-FISH and/or array-CGH. Flanking low-copy repeats may indicate a classical microdeletion syndrome genesis for the 2q37.3 microdeletion subgroup. Clinical evaluation revealed intellectual deficits and type E brachydactyly typical for classical AHO syndrome together with distinctive facial dysmorphisms not present in the former. Furthermore, one patient presented with schizophrenic psychosis, an observation that would be in accordance with previous reports about an association between schizophrenia susceptibility and an unknown gene within the chromosomal region 2q37.

The nicotinic acetylcholine receptor alpha 4 subunit contains a functionally relevant SNP Haplotype

BACKGROUND

Non-coding single nucleotide polymorphisms within the nicotinic acetylcholine receptor alpha 4 subunit gene (CHRNA4) are robustly associated with various neurological and behavioral phenotypes including schizophrenia, cognition and smoking. The most commonly associated polymorphisms are located in exon 5 and segregate as part of a haplotype. So far it is unknown if this haplotype is indeed functional, or if the observed associations are an indirect effect caused by linkage disequilibrium with not yet identified adjacent functional variants. We therefore analyzed the functional relevance of the exon 5 haplotype alleles.

RESULTS

Using voltage clamp experiments we were able to show that the CHRNA4 haplotype alleles differ with respect to their functional effects on receptor sensitivity including reversal of receptor sensitivity between low and high acetylcholine concentrations. The results indicate that underlying mechanisms might include differences in codon usage bias and changes in mRNA stability.

CONCLUSIONS

Our data demonstrate that the complementary alleles of the CHRNA4 exon 5 haplotype are functionally relevant, and might therefore be causative for the above mentioned associations.

Expression studies in gliomas and glial cells do not support a tumor suppressor role for LGI1

Disruptions of LGI1 in glioblastoma (GBM) cell lines and LGI1 mutations in families with autosomal dominant epilepsy imply a role for LGI1 in glial cells as well as in neurons. Although we and others could not find LGI1 mutations in malignant gliomas, our initial studies appeared to support the idea that LGI1 is poorly expressed or absent in these tumors. Microarray data suggested that LGI1 could be involved in the control of matrix metalloproteinases, and we found that tumors derived from U87 glioblastoma cells overexpressing LGI1 were less aggressive than U87 control tumors. To our surprise, we observed that LGI1 expression after differentiation of murine neural stem cells was robust in neurons but negligible in glial cells, in agreement with immunohistochemistry studies on rodent brain. This observation could suggest that the variable levels of LGI1 expression in gliomas reflect the presence of neurons entrapped within the tumor. To test this hypothesis, we investigated LGI1 expression in parallel with expression of the neuronal marker NEF3 by real-time PCR on 30 malignant gliomas. Results showed a strong, positive correlation between the expression levels of these two genes (P < 0.0001). Thus, our data confirm that LGI1 is involved in cell-matrix interactions but suggest that its expression is not relevant in glial cells, implying that its role as a tumor suppressor in gliomas should be reconsidered.

Characterization of human alpha 4 beta 2-nicotinic acetylcholine receptors stably and heterologously expressed in native nicotinic receptor-null SH-EP1 human epithelial cells

Naturally expressed nicotinic acetylcholine receptors composed of alpha4 and beta2 subunits (alpha4beta2-nAChR) are the predominant form of high affinity nicotine binding site in the brain implicated in nicotine reward, mediation of nicotinic cholinergic transmission, modulation of signaling through other chemical messages, and a number of neuropsychiatric disorders. To develop a model system for studies of human alpha4beta2-nAChR allowing protein chemical, functional, pharmacological, and regulation of expression studies, human alpha4 and beta2 subunits were stably introduced into the native nAChR-null human epithelial cell line SHEP1. Heterologously expressed alpha4beta2-nAChR engage in high-affinity, specific binding of 3H-labeled epibatidine (H-EBDN; macroscopic KD = 10 pM; kon = 0.74/min/nM, koff = 0.013/min). Immunofluorescence studies show alpha4 and beta2 subunit protein expression in virtually every transfected cell, and microautoradiographic studies show expression of 125I-labeled iodo-deschloroepibatidine binding sites in most cells. H-EBDN binding competition studies reveal high affinity for nicotinic agonists and lower affinity for nicotinic antagonists. Heterologously expressed alpha4beta2-nAChR functional studies using 86Rb+ efflux assays indicate full efficacy of epibatidine, nicotine, and acetylcholine; partial efficacy for 1,1-dimethyl-4-phenyl-piperazinium, cytisine, and suberyldicholine; competitive antagonism by dihydro-beta-erythroidine, decamethonium, and methyllycaconitine; noncompetitive antagonism by mecamylamine and eserine; and mixed antagonism by pancuronium, hexamethonium, and d-tubocurarine. These results demonstrate utility of transfected SH-EP1 cells as models for studies of human alpha4beta2-nAChR, and they also reveal complex relationships between apparent affinities of drugs for radioligand binding and functional sites on human alpha4beta2-nAChR.

Schizophrenia, psychotic illness and other psychiatric symptoms in families with autosomal dominant nocturnal frontal lobe epilepsy caused by different mutations

OBJECTIVES

Autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) is characterized by a strong family history of epileptic seizures, which predominantly occur during sleep. ADNFLE has been associated with mutations in two genes coding for the nicotinic acetylcholine receptor (CHRNA4 and CHRNB2). Thus far, three different mutations have been detected in the CHRNA4 gene, and two in the CHRNB2 gene. The aim of this study was to compare the frequency of psychiatric disorders in two ADNFLE families with different CHRNA4 mutations (776ins3 and Ser248Phe).

METHODS

Information was gathered from hospital charts and therapists, and the family members were assessed by clinical interviews and structured clinical interviews.

RESULTS

Of the 10 individuals diagnosed with epilepsy in the CHRNA4-776ins3 family, at least four had been in contact with psychiatric services. One individual had schizophrenia, while another family member had experienced at least two severe psychotic episodes, and had been taking antipsychotic medications for years. The third family member had been hospitalized at least three times for psychiatric problems. The fourth family member needs help with activities of daily living due to incapacitating apathy, although she does not have a psychiatric diagnosis. Such accumulation of psychiatric problems was not seen in the family with the Ser248Phe mutation.

CONCLUSION

These findings suggest that there may be an association between the 776ins3 mutation and the psychiatric symptoms, a hypothesis that needs further testing.

Recent advances in the diagnosis and treatment of epilepsy

Recent advances in the diagnosis and treatment of epilepsies are discussed with special consideration of epidemiology and classification, progress in neuroimaging, electrophysiological studies using EEG and MEG, initiation of medical and surgical treatment, the role of new antiepileptic drugs and selected aspects of genetics of idiopathic epilepsies. In addition from conclusions obtained by the review of recent developments suggestions for future work in Europe are discussed. A constructive approach from multicenter studies requires homologous definitions, documentations and standardization of procedures of trials for European multicenter studies.

New functions for nicotinic acetylcholine receptors?

Although the neuronal nicotinic acetylcholine receptor is found in most parts of the brain, not much is known about its functional significance. At least ten different subunits are expressed in the central nervous system, theoretically able to give rise to more than a thousand different receptor subtypes. Despite, or perhaps because of, this astonishing diversity, the biological role of this receptor type remains to be investigated. It has recently been found that a mutated alpha4-subunit is associated with an inherited epilepsy syndrome. A missense mutation replacing a serine in position 248 of the second transmembrane domain by phenylalanine leads to hypoactivity of the receptor due to accelerated desensitization and delayed resensitization. Thus, for the first time a link between a human disease and a mutated neuronal nicotinic acetylcholine receptor has been found, pointing to a possible involvement of this ligand-gated receptor family in the modulation of brain excitability levels.

Hippocampal malformation as a cause of familial febrile convulsions and subsequent hippocampal sclerosis

OBJECTIVE

One hypothesis proposes that a pre-existing alteration of medial temporal lobe structures contributes to febrile convulsions and subsequent hippocampal sclerosis (HS) in patients with temporal lobe epilepsy (TLE) and antecedent febrile convulsions. It is possible that such a structural alteration does not always lead to convulsions and may also be present in clinically unaffected relatives.

METHODS

We tested this hypothesis by MRI investigation of 23 members of two families, of whom 13 had experienced febrile convulsions and 10 had not. One member of each family with febrile convulsions subsequently developed TLE. We compared the right/left ratios of hippocampal volumes (RHV) with 23 age- and sex-matched controls. Additionally, two independent raters assessed hippocampal signal intensity and pattern in T2- and fluid-attenuated inversion recovery images.

RESULTS

Both TLE patients showed left HS. All subjects with febrile convulsions who did not develop epilepsy and six clinically unaffected relatives also showed asymmetric RHV (>3 standard deviation) but a normal hippocampal signal intensity. In all of these subjects, the left hippocampus was smaller. Visual inspection of these smaller hippocampi revealed blurred internal pattern or flat hippocampal bodies or both in one family and smaller hippocampal heads in the other. The pattern of HS in TLE patients showed a structural correlation with the abnormalities seen in their relatives. One subject with febrile convulsions had additional subcortical heterotopias.

CONCLUSION

These findings suggest a subtle, pre-existing hippocampal malformation that may facilitate febrile convulsions and contribute to the development of subsequent HS.

Possible association of a silent polymorphism in the neuronal nicotinic acetylcholine receptor subunit alpha4 with common idiopathic generalized epilepsies

The alpha4 subunit gene of the neuronal nicotinic acetylcholine receptor (CHRNA4) has recently been identified as the first gene underlying an idiopathic partial epilepsy syndrome in human, autosomal-dominant nocturnal frontal lobe epilepsy (ADNFLE). CHRNA4 is located in the candidate region for benign familial neonatal convulsions and low-voltage EEG on chromosome 20q. In the present study, we examined the possible role of CHRNA4 in common subtypes of idiopathic generalized epilepsy (IGE), comprising childhood and juvenile absence epilepsy and juvenile myoclonic epilepsy (JME), by systematically screening the coding region of the gene for sequence variants. We present here a population-based association study testing the hypothesis that variants of the CHRNA4 gene confer genetic susceptibility to common subtypes of IGE. The missense mutation (Ser248Phe), associated with ADNFLE, and four silent polymorphisms in the CHRNA4 gene were genotyped in 103 IGE patients and 92 controls by polymerase chain reaction and subsequent restriction analysis. Without correction for multiple testing, the frequency of the T-allele of the silent CfoI bp595 polymorphism was increased in the entire group of IGE patients (f(T) = 0.085) compared to that in the controls (f(T) = 0.027). The allelic association was not restricted to any subgroup of IGE with either JME or idiopathic absence epilepsies. This result suggests that variation of the CHRNA4 gene, or so-far-undetected sequence variants near the CHRNA4 locus, confer susceptibility to the common IGE syndromes.

An amino acid exchange in the second transmembrane segment of a neuronal nicotinic receptor causes partial epilepsy by altering its desensitization kinetics

The alpha4 subunit of the neuronal nicotinic acetylcholine receptor is the first gene shown to be involved in a human idiopathic epileptic disease. A missense mutation, leading to the replacement of serine 248 by phenylalanine in the second transmembrane segment, had been detected in patients with autosomal dominant nocturnal frontal lobe epilepsy. The properties of the wild type receptor composed of alpha4 and beta2 subunits and the mutant receptor where alpha4 subunits carried the mutation at serine 248 were compared by means of cDNA manipulation and expression in Xenopus oocytes. The mutant receptor exhibited faster desensitization upon activation by acetylcholine and recovery from the desensitized state was much slower than in the wild type receptor. We conclude that the reported mutation causes seizures via a diminution of the activity of the alpha4beta2 neuronal nicotinic acetylcholine receptor.

[Familial nocturnal frontal lobe epilepsy. Clinical aspects and genetics]

Autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) is a disease entity that has only recently been discovered. Its clinical variability and the frequently missed EEG features are probably some of the reasons why this disease is often overlooked or misdiagnosed. In a large Australian pedigree, a link was found between ADNFLE and polymorphic markers on chromosome 22q13.2-q13.3. Mutation analysis identified a mis-sense mutation in the gene coding for the alpha 4 subunit of the neuronal nicotinic acetylcholine receptor. The mutation was found in all affected family members. Thus, for the first time a likely relationship between an idiopathic epilepsy and a specific gene has been found. Additional studies will be needed to clarify the underlying pathologic mechanism. Furthermore, the hypothesis that other members of this multigene family are involved in epileptic diseases appears attractive.

Exon-intron structure of the human neuronal nicotinic acetylcholine receptor alpha 4 subunit (CHRNA4)

The human neuronal nicotinic acetylcholine receptor alpha 4 subunit gene (CHRNA4) is located in the candidate region for three different phenotypes: benign familial neonatal convulsions, autosomal dominant nocturnal frontal lobe epilepsy, and low-voltage EEG. Recently, a missense mutation in transmembrane domain 2 of CHRNA4 was found to be associated with autosomal dominant nocturnal frontal lobe epilepsy in one extended pedigree. We have determined the genomic organization of CHRNA4, which consists of six exons distributed over approximately 17 kb of genomic DNA. The nucleotide sequence obtained from the genomic regions adjacent to the exon boundaries enabled us to develop a set of primer pairs for PCR amplification of the complete coding region. The sequence analysis provides the basis for a comprehensive mutation screening of CHRNA4 in the above-mentioned phenotypes and possibly in other types of idiopathic epilepsies.

Detection of a CfoI polymorphism within exon 5 of the human neuronal nicotinic acetylcholine receptor alpha 4 subunit gene (CHRNA4)

The gene coding for the alpha 4 subunit of the neuronal nicotinic acetylcholine receptor (CHRNA4) has been recently mapped in the candidate region for benign familial neonatal convulsions (BFNC) on chromosome 20q13.2-q13.3. The region is only partially covered with polymorphic markers, and so far no PCR-based polymorphisms have been described in the critical region for BFNC. We now report the first polymorphic marker in the coding region of CHRNA4. The new marker, which is detected by PCR, will be useful for evaluation of the role of CHRNA4 as a candidate gene for BFNC. It will further enable the investigation of this important brain-specific gene in association studies with different types of epileptic diseases and other neurological disorders.

Benign familial neonatal convulsions: confirmation of genetic heterogeneity and further evidence for a second locus on chromosome 8q

The syndrome of benign familial neonatal convulsions (BFNC) is a rare, autosomal dominant form of epilepsy. It is characterized by spontaneous seizures beginning within the first 6 months of life. In the majority of families linkage is to chromosome 20q markers. Based on the linkage results in one large BFNC kindred, genetic heterogeneity and existence of a second locus on chromosome 8 have been suggested. Here we report on a second BFNC family in which linkage to the EBN1 locus on chromosome 20q was excluded, confirming the genetic heterogeneity of this disorder. All affected family members experienced onset of seizures before the age of 2 months. Three BFNC subjects showed subsequent epileptic seizures after 12 months of age, showing that the risk of subsequent epilepsy is not restricted to the chromosome 20q linked BFNC families. A lod score of 0.99 was obtained with the marker D8S274, suggesting linkage to chromosome 8.

A nonsense mutation in the alpha4 subunit of the nicotinic acetylcholine receptor (CHRNA4) cosegregates with 20q-linked benign neonatal familial convulsions (EBNI)

Benign Familial Neonatal Convulsions (BFNC) is an epileptic disorder with an autosomal dominant mode of transmission. It has been shown that about 80% of BFNC pedigrees are linked to a genetic defect on chromosome 20q13.3. A candidate gene for the epilepsies, the gene coding for the alpha4 subunit of the nicotinic cholinergic receptor (CHRNA4), has previously been localized on chromosome 20. Here we report a single point mutation converting a serine codon to a stop codon in the exon 5 of CHRNA4, in one BFNC family. Identification of CHRNA4 as the defective gene in 20q-BFNC represents the first example of a human idiopathic epilepsy caused by a mutation directly affecting a neurotransmitter receptor in the central nervous system.

A genetic study of the human low-voltage electroencephalogram

The studied phenotype, the low-voltage electroencephalogram (LVEEG), is characterized by the absence of an alpha rhythm from the resting EEG. In previous studies, evidence was found for a simple autosomal-dominant mode of inheritance of the LVEEG. Such a polymorphism in brain function can be used as a research model for the stepwise elucidation of the molecular mechanism involved in those aspects of neuronal activity that are reflected in the EEG. Linkage with the variable number of tandem repeats (VNTR) marker CMM6 (D20S19) and localization of an LVEEG (EEGV1) gene on 20q have previously been reported, and genetic heterogeneity has been demonstrated. This latter result has been corroborated by studying new marker (MS214). The phenotype of the LVEEG is described here in greater detail. Its main characteristic is the absence of rhythmic alpha activity, especially in occipital leads, whereas other wave forms such as beta or theta waves may be present. Analysis of 17 new families (some of them large), together with 60 previously described nuclear families, supports the genetic hypothesis of an autosomal-dominant mode of inheritance. Problems connected with the analysis of linkage heterogeneity, exclusion mapping, and the study of multipoint linkage are discussed. A possible explanation of the localization of LVEEG in the close vicinity of another gene influencing synchronization of the normal EEG, the gene for benign neonatal epilepsie, is given.

D20S19, linked to low voltage EEG, benign neonatal convulsions, and Fanconi anaemia, maps to a region of enhanced recombination and is localized between CpG islands

Recent linkage studies located genes responsible for the low voltage EEG, benign neonatal convulsions and for the Fanconi anaemia to the vicinity of the VNTR marker CMM6 (D20S19). Physical mapping experiments using pulsefield electrophoresis in the distal part of chromosome 20q were chosen as a first step towards cloning of these genes. The observed pattern of shared fragments lead to the locus order 'tel-IP20K09-RMR6-CMM6-MS214-cen', which differs from previously reported genetic linkage maps. The physical intervals between these probes are markedly shorter compared with the genetic distances. Clusters of rare cutter sites around CMM6 point to at least four closely related CpG islands.

Localization of a gene for the human low-voltage EEG on 20q and genetic heterogeneity

The localization of a gene responsible for a normal variant of the human electroencephalogram to the distal part of chromosome 20q is reported. A linkage analysis, including 17 families with 191 individuals, tested with 73 RFLPs and 22 blood and serological markers, was performed for the low-voltage electroencephalogram. This is a normal variant of the human electroencephalogram with an autosomal dominant mode of inheritance. The results present strong evidence for close linkage with the highly polymorphic marker CMM6 (D20S19) and for genetic heterogeneity.

Tapetoretinal degeneration in brothers with apparent Cohen syndrome: nosology with Mirhosseini-Holmes-Walton syndrome

We report on 2 brothers with marked eye anomalies, documented with histopathological studies, and several other findings fitting the diagnosis of both the Cohen and the Mirhosseini-Holmes-Walton syndromes. In accordance with Norio and Raitta (Norio R, Raitta C (1986): Am J Med Genet 25:397-398) we come to the conclusion that these 2 syndromes constitute one clinical but possibly heterogeneous entity.

Differential release of [3H]acetylcholine from the rat phrenic nerve-hemidiaphragm preparation by electrical nerve stimulation and by high potassium

Neuronal transmitter stores of the phrenic nerve were labelled under different conditions. Subsequently, transmitter release evoked by electrical nerve stimulation and by a high potassium-low sodium solution was studied. Incubation of the end-plate preparation with [3H]choline at rest led to the synthesis of [3H]acetylcholine which could not be released by electrical nerve stimulation but it was released by high potassium-low sodium solution, independent of the presence of extracellular calcium. When the end-plate preparation was labelled during stimulation at 1 Hz, prolonged periods of electrical nerve stimulation released 83% of the total releasable [3H]transmitter pool in a completely calcium-dependent manner. After exhaustion of the electrically releasable pool, high potassium-low sodium solution still caused a significant outflow. Without a preceding exhaustion of the [3H]acetylcholine pool, high potassium-low sodium solution released a similar amount in the absence of extracellular calcium or after pretreatment with the intracellular calcium chelating substance, Quin-2. When evoked transmitter release was studied at different temperatures (36, 26 and 16 degrees C) Q 10 values of 1.6 and 1.0 were found for the release caused by electrical nerve stimulation and high potassium-low sodium solution (calcium-independent effect), respectively. After labelling during a short interval (2 min) but at a high stimulation rate (50 Hz), only 72% of the releasable [3H]transmitter could be released by electrical nerve stimulation, whereas the outflow due to the calcium-independent effect of high potassium-low sodium solution increased from 17 (labelling during stimulation at 1 Hz) to 28%. It is suggested that the calcium-independent effect of high potassium-low sodium solution reflects the release of acetylcholine from the cytoplasmic compartment, as this outflow occurred after labelling at rest and increased when cytoplasmic synthesis was enhanced by a high loading stimulation. In contrast to high potassium-low sodium solution, propagated nerve activity cannot release acetylcholine synthesized at rest (presumed to be cytoplasmic), but only [3H]acetylcholine synthesized during quantal release (presumed to be vesicular). The absolute requirement of extracellular calcium for electrically stimulated release suggests an exocytotic release mechanism. The low Q 10 value of 1.6 does not fit into the concept of a carrier- or channel-operated release mechanism.(ABSTRACT TRUNCATED AT 400 WORDS)