Candidate gene association study for noise-induced hearing loss in two independent noise-exposed populations

Millions of people are daily exposed to high levels of noise. Consequently, noise-induced hearing loss (NIHL) is one of the most important occupational health hazards worldwide. In this study, we performed an association study for NIHL based on a candidate gene approach. 644 Single Nucleotide Polymorphisms (SNPs) in 53 candidate genes were analyzed in two independent NIHL sample sets, a Swedish set and part of a Polish set. Eight SNPs with promising results were selected and analysed in the remaining part of the Polish samples. One SNP in PCDH15 (rs7095441), resulted in significant associations in both sample sets while two SNPs in MYH14 (rs667907 and rs588035), resulted in significant associations in the Polish sample set and significant interactions with noise exposure level in the Swedish sample set. Calculation of odds ratios revealed a significant association of rs588035 with NIHL in the Swedish high noise exposure level group. Our studies suggest that PCDH15 and MYH14 may be NIHL susceptibility genes, but further replication in independent sample sets is mandatory.

Contribution of the N-acetyltransferase 2 polymorphism NAT2*6A to age-related hearing impairment

BACKGROUND

Age-related hearing impairment (ARHI) is the most common sensory impairment in older people, affecting 50% of those aged 80 years. The proportion of older people is increasing in the general population, and as a consequence, the number of people affected with ARHI is growing. ARHI is a complex disorder, with both environmental and genetic factors contributing to the disease. The first studies to elucidate these genetic factors were recently performed, resulting in the identification of the first two susceptibility genes for ARHI, NAT2 and KCNQ4.

METHODS

In the present study, the association between ARHI and polymorphisms in genes that contribute to the defence against reactive oxygen species, including GSTT1, GSTM1 and NAT2, was tested. Samples originated from seven different countries and were combined into two test population samples, the general European population and the Finnish population. Two distinct phenotypes for ARHI were studied, Z(low) and Z(high), representing hearing in the low and high frequencies, respectively. Statistical analysis was performed for single polymorphisms (GSTM1, GSTT1, NAT2*5A, NAT2*6A, and NAT2*7A), haplotypes, and gene-environment and gene-gene interactions.

RESULTS

We found an association between ARHI and GSTT1 and GSTM1 in the Finnish population sample, and with NAT2*6A in the general European population sample. The latter finding replicates previously published data.

CONCLUSION

As replication is considered the ultimate proof of true associations in the study of complex disorders, this study provides further support for the involvement of NAT2*6A in ARHI.

Prevalence of tinnitus and audiometric shape

OBJECTIVES

Studies of tinnitus are often conducted on patient populations presenting for treatment. It is, however, difficult to generalise prevalence numbers and aetiological results from these studies to a healthy, elderly population. The first aim of our study was to determine the prevalence of tinnitus in an otologically screened population between 55 and 65 years old. Secondly, both prevalence and the specific characteristics of tinnitus were compared in subjects with either a flat audiogram, a high-frequency gently sloping audiogram or a high-frequency steeply sloping audiogram.

METHODS

1147 subjects (549 males and 598 females) were recruited through population registers and underwent thorough clinical and audiological examinations. Subjects who reported tinnitus in the general questionnaire about medical history and environmental exposure were invited to complete an additional questionnaire on tinnitus history.

RESULTS

The prevalence of tinnitus was 19.3% according to the general questionnaire on medical health and environmental exposure and 11.8% according to the additional detailed tinnitus-specific questionnaire. Furthermore, our results indicate that gender has a significant effect (tinnitus is more common in males than in females), as does audiometric configuration (tinnitus is more common in subjects with a high-frequency steeply sloping audiogram than in subjects with a flat audiogram). Both effects were significant in noise-/solvent-exposed subjects, as well as in non-exposed subjects. Finally, comparison of "tinnitus characteristics" in subjects categorised by audiogram configuration revealed significant differences in loudness, pitch, temporal variability and family history of tinnitus.

Familial aggregation of tinnitus: a European multicentre study

INTRODUCTION AND AIM

Tinnitus is a common condition affecting approximately 20% of the older population. There is increasing evidence that changes in the central auditory system following cochlear malfunctioning are responsible for tinnitus. To date, few investigators have studied the influence of genetic factors on tinnitus. The present report investigates the presence of a familial effect in tinnitus subjects.

METHODS

In a European multicentre study, 198 families were recruited in seven European countries. Each family had at least 3 siblings. Subjects were screened for causes of hearing loss other than presbyacusis by clinical examination and a questionnaire. The presence of tinnitus was evaluated with the question "Nowadays, do you ever get noises in your head or ear (tinnitus) which usually last longer than five minutes". Familial aggregation was tested using three methods: a mixed model approach, calculating familial correlations, and estimating the risk of a subject having tinnitus if the disorder is present in another family member.

RESULTS

All methods demonstrated a significant familial effect for tinnitus. The effect persisted after correction for the effect of other risk factors such as hearing loss, gender and age. The size of the familial effect is smaller than that for age-related hearing impairment, with a familial correlation of 0.15.

CONCLUSION

The presence of a familial effect for tinnitus opens the door to specific studies that can determine whether this effect is due to a shared familial environment or the involvement of genetic factors. Subsequent association studies may result in the identification of the factors responsible. In addition, more emphasis should be placed on the effect of role models in the treatment of tinnitus.

KCNQ4: a gene for age-related hearing impairment?

Age-related hearing impairment (ARHI) is the most common sensory impairment among the elderly. It is a complex disorder influenced by genetic as well as environmental factors. SNPs in a candidate susceptibility gene, KCNQ4, were examined in two independent Caucasian populations. Two quantitative trait locus (QTL) values were investigated: Zhigh and Zlow, a measure of high and respectively low frequency hearing loss. In the first population, the statistical analysis of 23 genotyped SNPs spread across KCNQ4 resulted in significant p-values for two SNPs for Zhigh-SNP9 (NT_004511:g.11244177A > T) and SNP15 (NT_004511:g.11257005C > T; NP_004691:p.Ala259Ala), and one SNP for Zlow-SNP12 (NT_004511:g.11249550A > T). The linkage disequilibrium (LD) structure of KCNQ4 was subsequently determined in a 34-kb region surrounding the significant SNPs, resulting in three LD-blocks. LD-block 1 contains SNP9 and covers an area of 5 kb, LD-block 2 measures 5 kb and surrounds SNP13 (NT_004511:g.11253513A > G) to SNP18 (NT_004511:g.11257509G > A; NP_004691:p.Thr293Thr), and LD-block 3 spans 7 kb. Five tag-SNPs of block 1 and 2, and 2 extra SNPs were subsequently genotyped in the second population. Again, several SNPs were positively associated with ARHI: one SNP (SNP18) for the high frequencies and three SNPs (SNP9, SNP12, and SNP18) for the low frequencies, although only a single SNP (SNP12) resulted in significant p-values in both populations. Nevertheless, the associated SNPs of both populations were all located in the same 13-kb region in the middle of the KCNQ4 gene.

Evaluation of the role of the SQSTM1 gene in sporadic Belgian patients with Paget's disease

A positional cloning effort in French Canadian families with Paget's disease of bone (PDB) resulted in the identification of a mutation in the sequestosome1 (SQSTM1) gene in a subset of both familial and sporadic PDB cases. This was confirmed in samples of mainly United Kingdom (UK) origin. In this study, we performed both mutation analysis and association studies in order to evaluate the role of this gene in a collection of isolated Belgian PDB patients. A mutation in the SQSTM1 gene was found in only 6 of 111 patients (5.4%). In all cases it involves the P392L mutation, previously shown to be common in both familial and sporadic cases. To perform association studies, we selected 8 single nucleotide polymorphisms (SNPs) and looked for linkage disequilibrium (LD) between these. Haplotype analysis indicated that typing of 3 Tag SNPs (IVS1 + 633A/C, IVS5 - 23A/G, and 976A/G) enables us to identify the most common haplotypes. Association studies for the 3 selected SNPs, based on 105 PDB cases without a SQSTM1 mutation and 159 control individuals, did not support a possible influence of natural variants in the SQSTM1 gene either on the pathogenesis of PDB or on the disease severity. In conclusion, our study confirms that the P392L mutation is a recurrent mutation causing PDB in different populations. We were not able to show an association between SQSTM1 polymorphisms and PDB in our population but this clearly needs to be extended to other populations. The presented identification of haplotype Tag SNPs will be of major help for such studies.

Interpretation of pure-tone thresholds in sensorineural hearing loss (SNHL): a review of measurement variability and age-specific references

When assessing a patient with a sensorineural hearing impairment, the most simple and most widely available technical investigation is pure-tone audiometry. Although it is a subjective measure, the test is very reliable if the patient is cooperative. In this paper we review standards and test-retest reliability for pure-tone audiometry. A pure-tone threshold measurement at a single frequency has a chance of 90% to be repeated between -10 dB and +10 dB compared to the first measurement, assuming no real change in hearing thresholds has occurred. It is also of great importance to use correct gender- and age-specific reference values when interpreting pure-tone threshold measurements. Several large-scale epidemiological studies have been conducted during recent years, and have provided us with reliable gender- and age-specific references. A method to take into account the age-related deterioration is presented. In this method, Z-score audiograms represent traditional thresholds in an age- and gender-independent way. At each frequency, the Z-score value is the number of standard deviation units that the threshold differs from the median value for the otologically normal population (ISO 7029).

Hereditary cochleovestibular dysfunction due to a COCH gene mutation (DFNA9): a follow-up study of a family

Cochleovestibular impairment was evaluated, in relation to age, in a longitudinal follow-up study on a Dutch family with a DFNA9 trait caused by a Pro51Ser mutation in the COCH gene on chromosome 14q12-q13. Fourteen cases were genotyped. The onset age of progressive impairment reported by the mutation carriers was between age 35 and 45 years. Pure-tone thresholds deteriorated by about 2-7 dB per year (mean 3.8 dB per year) in a variable, often asymmetrical, fashion. One mutation carrier developed recurrent episodes of vertigo accompanied by nausea and vomiting, resembling Ménière's disease. Two others developed special susceptibility for motion sickness and appeared to have a hyperactive vestibulo-ocular reflex. More advanced stages of vestibular impairment, i.e. vestibular hyporeflexia and complete vestibular areflexia, were eventually found in a number of cases. DFNA9/COCH should be considered as a possible cause in patients developing combined progressive cochlear and vestibular impairment, or suspected hereditary Ménière-like disease, from around middle age.

Hereditary otovestibular dysfunction and Ménière's disease in a large Belgian family is caused by a missense mutation in the COCH gene

OBJECTIVE

To report the clinical, auditory, and vestibular characteristics of a nonsyndromic otovestibular dysfunction in a large Belgian family caused by a missense mutation of the DFNA9 gene: COCH.

STUDY DESIGN

Retrospective study of the clinical, audiologic, and vestibular data of 60 genetically affected cases.

SETTING

Tertiary referral center.

PATIENTS

All members of a Belgian kindred who carry the genetic (P51S) defect linked to the inherited hearing and vestibular impairment.

INTERVENTIONS

Diagnostic otologic, audiometric, and vestibular analysis and imaging.

MAIN OUTCOME MEASURES

Pure tone audiometry, supraliminary audiometry. and vestibular investigation.

RESULTS

The autosomal dominant inherited impairment was characterized by peripheral degeneration of the inner ear, leading to total deafness and bilateral vestibular areflexia.

CONCLUSIONS

The genetically affected persons of a Belgian family shared a progressive sensorineural hearing loss starting between the third and sixth decade. Vestibular symptoms started at about the same age as the hearing loss. The vestibular symptoms consisted of instability in darkness, a tendency to fall sideways, light-headiness, a drunken feeling, and attacks of vertigo. Most of the patients reported tinnitus, and half of them reported pressure in the ears. Clinically, 9 of the 60 patients met the criteria for definite Ménière's disease, and another 13 and 17 patients met the criteria for probable or possible Ménière's disease, respectively. All 9 were older than the age of 35, but only 1 was older than 55 years, so more than 30% of the patients were between 35 and 55 years old. A specific pattern could be recognized in the evolution of the otovestibular impairment. Under the age of 35 years, almost all the affected family members had normal hearing, whereas above the age of 55 years, the hearing loss was at least moderate, and vestibular hypofunction occurred. In between, there was a transition period of two to three decades, when deterioration of the cochleovestibular function occurred, with a temporary audiometric and vestibular asymmetry.

A common founder for the 35delG GJB2 gene mutation in connexin 26 hearing impairment

Fifty to eighty percent of autosomal recessive congenital severe to profound hearing impairment result from mutations in a single gene, GJB2, that encodes the protein connexin 26. One mutation of this gene, the 35delG allele, is particularly common in white populations. We report evidence that the high frequency of this allelic variant is the result of a founder effect rather than a mutational hot spot in GJB2, which was the prevailing hypothesis. Patients homozygous for the 35delG mutation and normal hearing controls originating from Belgium, the UK, and the USA were genotyped for different single nucleotide polymorphisms (SNPs). Four SNPs mapped in the immediate vicinity of GJB2, while two were positioned up to 76 kb from it. Significant differences between the genotypes of patients and controls for the five SNPs closest to GJB2 were found, with nearly complete association of one SNP allele with the 35delG mutation. For the most remote SNP, we could not detect any association. We conclude that the 35delG mutation is derived from a common, albeit ancient founder.

Long-term potentiation in mice lacking the neural cell adhesion molecule L1

Genetic evidence indicates that cell adhesion molecules of the immunoglobulin superfamily (IgCAMs) are critical for activity-dependent synapse formation at the neuromuscular junction in Drosophila and have also been implicated in synaptic remodelling during learning in Aplysia (see [1] for review). In mammals, a widely adopted model for the process of learning at the cellular level is long-term potentiation (LTP) in the hippocampal formation. Studies in vitro have shown that antibodies to the IgCAMs L1 and NCAM reduce LTP in CA1 neurons of rat hippocampus, suggesting a role for these molecules in the modulation of synaptic efficacy, perhaps by regulating synaptic remodelling [2]. A role for NCAM in LTP has been confirmed in mice lacking NCAM [3] (but see [4]), but similar studies have not been reported for L1. Here we examine LTP in the hippocampus of mice lacking L1 [5,6], using different experimental protocols in three different laboratories. In tests of LTP in vitro and in vivo we found no significant differences between mutant animals and controls. Thus, contrary to expectation, our data suggest that L1 function is not necessary for the establishment or maintenance of LTP in the hippocampus. Impaired performance in spatial learning exhibited by L1 mutants may therefore not be due to hippocampal dysfunction [6].

Familial progressive vestibulocochlear dysfunction caused by a COCH mutation (DFNA9)

OBJECTIVE

To describe the decline of vestibulocochlear function in a man with vestibulocochlear dysfunction caused by a Pro51Ser mutation within the COCH gene on chromosome 14q12-13 (DFNA9).

METHODS

A follow-up of more than 15 years was performed in a single case. Clinical investigations were supplemented by oculomotor, vestibular, and auditory tests.

RESULTS

A 50-year-old man had had progressive sensorineural hearing loss and dysequilibrium for 15 years; he had been asymptomatic at the age of 35 years. He suffered from instability in the dark, head movement-dependent oscillopsia, paroxysmal positional vertigo, and vertigo with and without nausea. Hearing impairment started unilaterally, predominantly in the high frequencies. He also reported tinnitus. Disease progressed to severe bilateral high-frequency hearing impairment and vestibular areflexia. Fluctuation of vestibulocochlear function was documented and mentioned by the patient.

CONCLUSIONS

Our patient proved to suffer from an autosomal dominant vestibulocochlear disorder caused by a COCH gene mutation. The remarkable medical history has some features in common with Meniere disease; however, there are also different clinical and neurophysiological features. In the family, phenotypic variability is present.

Computational modeling of entorhinal cortex

Computational modeling provides a means for linking the physiological and anatomical characteristics of entorhinal cortex at a cellular level to the functional role of this region in behavior. We have developed detailed simulations of entorhinal cortical neurons and networks, with an emphasis on the role of acetylcholine in entorhinal cortical function. Computational modeling suggests that when acetylcholine levels are high, this sets appropriate dynamics for the storage of stimuli during performance of delayed matching tasks. In particular, acetylcholine activates a calcium-sensitive nonspecific cation current which provides an intrinsic cellular mechanism which could maintain neuronal activity across a delay period. Simulations demonstrate how this phenomena could underlie entorhinal cortex delay activity as described in previous unit recordings. Acetylcholine also induces theta rhythm oscillations which may be appropriate for timing of afferent input to be encoded in hippocampus and for extraction of individual stored sequences from multiple stored sequences. Lower levels of acetylcholine may allow sharp wave dynamics which can reactivate associations encoded in hippocampus and drive the formation of additional traces in hippocampus and entorhinal cortex during consolidation.

Impact of blood transfusions on inflammatory mediator release in patients undergoing cardiac surgery

STUDY OBJECTIVES

This study was conducted to investigate whether intraoperative blood transfusions affect the release of proinflammatory mediators in patients undergoing cardiac surgery. Therefore, we measured plasma levels of bactericidal permeability increasing protein (BPI) as a marker of neutrophil activation, interleukin-6 (IL-6), lipopolysaccharide binding protein (LBP), and C-reactive protein (CRP). In addition, these mediators, except CRP, were also measured in packed red cell units (PCs) administered to these patients.

DESIGN

Prospective study.

SETTING

Cardiopulmonary surgery department in a university hospital.

PATIENTS

One hundred fourteen consecutive patients undergoing cardiac surgery.

INTERVENTIONS

Blood samples were taken at induction of anesthesia, at the start of aortic cross-clamping, at aortic unclamping, and at 0.5, 4, 8, and 18 h thereafter.

RESULTS

Thirty-six patients received PC intraoperatively. BPI levels in patients who received transfusions were significantly higher at 0.5 and 4 h after aortic unclamping than in patients without transfusions (p < 0.05), and increased with the number of PC administered. IL-6 levels at 0.5, 4, and 18 h after aortic unclamping were also significantly higher in patients who received transfusions (p < 0.01). BPI was found in all units of packed red cells tested at concentrations up to 15 times preoperative plasma levels in patients. However, PC IL-6 could be detected in none of the samples. Plasma levels of LBP and CRP were similar in both patient groups. LBP was found in very low concentrations in all PC. Patients who received intraoperative transfusions had a worse postoperative performance.

CONCLUSIONS

Intraoperative PC transfusions do contribute to the inflammatory response after cardiac surgery both by enhancing part of the response and by directly changing plasma concentrations of inflammatory mediators. Furthermore, these data show that intraoperative PC transfusion is associated with a worse postoperative performance.

The COCH gene: a frequent cause of hearing impairment and vestibular dysfunction?

The identification of genes leading to hereditary hearing impairment is one of the ways to elucidate the functioning of the inner ear. Over the past few years, several genes responsible for non-syndromal hereditary hearing impairment have been identified. One of these genes, named COCH, is responsible for autosomal dominant progressive sensorineural hearing loss associated with vestibular impairment (DFNA9). Histopathological analysis in patients with a COCH mutation revealed the presence of an acidophylic mucopolysaccharide deposit in the inner ear. An overview of the clinical, pathological and genetic studies on COCH is given, and the possible role of COCH in the pathology of DFNA9 is discussed.

Patterns of p53 gene mutations in head and neck cancer: full-length gene sequencing and results of primary radiotherapy

p53 gene alterations are common in head and neck cancers, but their prognostic value has not been clearly established. Despite evidence in other cancers that sequencing of the entire p53 coding region provides prognostic information, full-length p53 gene sequencing has rarely been performed in head and neck cancers. In this study, p53 was assessed in a series of 42 pretreatment biopsies from patients with laryngeal carcinomas by full-length gene sequencing and by immunohistochemistry (IHC). Associations among p53 genotype, protein expression, and local recurrence were assessed in 35 irradiated patients followed for a minimum of 5 years. DNA was extracted from formalin-fixed, paraffin-embedded biopsies, and exons 2-11 of the p53 gene were individually amplified by PCR and then directly sequenced. IHC was performed to detect mutant and wild-type p53 protein using the DO7 monoclonal antibody. p21 protein expression was assessed using the EA1 monoclonal antibody. Twenty genetic alterations were observed in 42 tumors (48%). Four of these alterations (20%) occurred outside exons 5-8. There was a significant association between p53 gene and protein status (chi2 = 4.18, P = 0.04), although the correlation was weak (phi coefficient = -0.327). Although local relapse following radiation was significantly associated with nodal status, no correlations were observed between p53 status (gene or IHC) and local recurrence following radiation therapy, based on the Kaplan-Meier method. These results show that p53 mutations are common in laryngeal carcinomas and that a proportion occur outside traditionally examined regions. The lack of correlation between p53 status and local control suggests that this marker is not as powerful as traditional prognostic factors, such as lymph node status.

High prevalence of symptoms of Menière's disease in three families with a mutation in the COCH gene

We report the genetic analysis of one large Belgian and two small Dutch families with autosomal dominant non-syndromic progressive sensorineural hearing loss associated with vestibular dysfunction. Linkage studies in the Belgian family mapped the disease to the DFNA9 locus on chromosome 14. Mutation analysis of the COCH gene, which is responsible for DFNA9, revealed a missense mutation changing a highly conserved residue. One of the patients, who had an earlier age of onset in comparison with most of the affected family members, was shown to be homozygous for the mutation. After the mutation was found in the Belgian family, we discovered that the same missense mutation was also present in two Dutch families with similar cochleo-vestibular symptoms. In all three families with hearing loss and imbalance problems, >25% of the patients showed additional symptoms, including episodes of vertigo, tinnitus, aural fullness and hearing loss. Clinically, these symptoms are consistent with the criteria for Menière's disease. The importance of genetic factors in Menière's disease has been suggested on many occasions, but this study is the first report of a mutation in a gene leading to the symptoms of Menière's disease in a significant portion of the carriers. The COCH gene may be one of the genetic factors contributing to Menière's disease and the possibility of a COCH mutation should be considered in patients with Menière's disease symptoms.

Dependence of the ligation efficiency of large DNA fragments isolated from agarose gels on the purification method

The isolation of large DNA fragments (> 5 kb) from agarose gels can be problematic. The DNA yield is often low, and the purification may be insufficient for subsequent reactions such as sequencing or ligation. Here we have compared a number of commonly used methods and commercial kits for DNA recovery. Large DNA fragments (12 and 14 kb, respectively) were isolated from agarose gel and purified, the recovery yield was tested, and a well-defined amount of purified DNA was used in a standard ligation reaction. We observed dramatic differences in the efficiency of this ligation reaction depending on which recovery method had been used. However, the respective ligation efficiencies of the different methods were not related to their recovery yields.

Familial congenital hydrocephalus and aqueduct stenosis with probably autosomal dominant inheritance and variable expression

A kindred is reported on with suspected autosomal dominant congenital hydrocephalus and aqueduct stenosis. In contrast to patients with X-linked congenital hydrocephalus with stenosis of the aqueduct of Sylvius (HSAS) our patients were not mentally retarded and they did not show any pyramidal tract dysfunction or clasped thumbs; the pyramids were not affected either, as was confirmed by autopsy, CT or MRI. Molecular genetic studies in our patients have not revealed abnormalities of eight exons of the L1 neural adhesion molecule gene that is related to HSAS.

L1 knockout mice show dilated ventricles, vermis hypoplasia and impaired exploration patterns

L1 is a neural cell adhesion molecule mainly involved in axon guidance and neuronal migration during brain development. Mutations in the human L1 gene give rise to a complex clinical picture, with mental retardation, neurologic abnormalities and a variable degree of hydrocephalus. Recently, a transgenic mouse model with a targeted null mutation in the L1 gene was generated. These knockout (KO) mice show hypoplasia of the corticospinal tract. Here we have performed further studies of these KO mice including magnetic resonance imaging of the brain, neuropathological analysis and behavioral testing. The ventricular system was shown to be abnormal with dilatation of the lateral ventricles and the 4th ventricle, and an altered shape of the Sylvius aqueduct. Additionally, the cerebellar vermis of the KO mice is hypoplastic. Their exploratory behavior is characterized by stereotype peripheral circling reminiscent of that of rodents with induced cerebellar lesions.

Systemic inflammation present in patients undergoing CABG without extracorporeal circulation

STUDY OBJECTIVES

This study was conducted to evaluate to what extent the cardiopulmonary bypass (CPB) procedure in patients undergoing coronary artery bypass grafting (CABG) contributes to the systemic inflammatory response. Therefore, we measured bactericidal permeability increasing protein (BPI) as an indicator of neutrophil activation, interleukin 6 as inducer of the acute phase response, and lipopolysaccharide binding protein and C-reactive protein as parameters of the acute phase response in patients undergoing CABG either with or without the use of CPB.

DESIGN

Prospective study.

SETTING

Cardiopulmonary surgery department in a university hospital.

PATIENTS

Sixteen patients undergoing elective CABG were included. Eight patients underwent surgery with CPB, and eight patients underwent surgery without CPB (non-CPB).

INTERVENTIONS

In the CPB group, blood samples were taken upon induction of anesthesia, at the start of aortic cross-clamping, at aortic unclamping, and 0.5, 4, 8, and 18 h thereafter. In the non-CPB group, blood samples were taken upon induction of anesthesia, and 0.5, 4, 8, and 18 h after completion of the bypass graft anastomoses.

MEASUREMENTS AND RESULTS

BPI release from neutrophil granules markedly increased during surgery in CPB patients but not in non-CPB patients. The increase in acute phase reactants, however, was the same in both patient groups.

CONCLUSIONS

These data indicate that the acute phase response in CABG patients, which has historically been ascribed to the CPB procedure, is predominantly caused by the surgical procedure per se. Early neutrophil activation, however, is seen only when extracorporeal circulation is used.

Genotype-phenotype correlation in L1 associated diseases

The neural cell adhesion molecule L1 (L1CAM) plays a key role during embryonic development of the nervous system and is involved in memory and learning. Mutations in the L1 gene are responsible for four X linked neurological conditions: X linked hydrocephalus (HSAS), MASA syndrome, complicated spastic paraplegia type 1 (SP-1), and X linked agenesis of the corpus callosum. As the clinical picture of these four L1 associated diseases shows considerable overlap and is characterised by Corpus callosum hypoplasia, mental Retardation, Adducted thumbs, Spastic paraplegia, and Hydrocephalus, these conditions have recently been lumped together into the CRASH syndrome. We investigate here whether a genotype-phenotype correlation exists in CRASH syndrome since its clinical spectrum is highly variable and numerous L1 mutations have been described. We found that (1) mutations in the extracellular part of L1 leading to truncation or absence of L1 cause a severe phenotype, (2) mutations in the cytoplasmic domain of L1 give rise to a milder phenotype than extracellular mutations, and (3) extracellular missense mutations affecting amino acids situated on the surface of a domain cause a milder phenotype than those affecting amino acids buried in the core of the domain.