In search of genetic constraints limiting the evolution of egg size: direct and correlated responses to artificial selection on a prenatal maternal effector.

Maternal effects are an important force in nature, but the evolutionary dynamics of the traits that cause them are not well understood. Egg size is known to be a key mediator of prenatal maternal effects with an established genetic basis. In contrast to theoretical expectations for fitness-related traits, there is a large amount of additive genetic variation in egg size observed in natural populations. One possible mechanism for the maintenance of this variation is through genetic constraints caused by a shared genetic basis among traits. Here we created replicated, divergent selection lines for maternal egg investment in Japanese quail (Coturnix japonica) to quantify the role of genetic constraints in the evolution of egg size. We found that egg size responds rapidly to selection, accompanied by a strong response in all egg components. Initially, we observed a correlated response in body size, but this response declined over time, showing that egg size and body size can evolve independently. Furthermore, no correlated response in fecundity (measured as the proportion of days on which a female laid an egg) was observed. However, the response to selection was asymmetrical, with egg size plateauing after one generation of selection in the high but not the low investment lines. We attribute this pattern to the presence of genetic asymmetries, caused by directional dominance or unequal allele frequencies. Such asymmetries may contribute to the evolutionary stasis in egg size observed in natural populations, despite a positive association between egg size and fitness.

[Lynch syndrome: when pathologist and clinician have the opportunity to reduce the risk of developing cancer]. / Le syndrome de lynch: pathologiste et praticien peuvent ensemble éduire le risque de cancer.

Lynch syndrome is an autosomal dominant disease associated with an important risk of cancer, mainly endometrial and colorectal-cancer. This risk can be efficiently lessen by an appropriate screening as far as the mutations carriers are identified. As current clinicopathological recommendations lack sensitivity, a systematic pre-screening of every patient with a colorectal or endometrial cancer can be proposed. Oncogenetic units of the HUG in Geneva and ICHV in Valais have set up a population-based study to evaluate the efficacy of such a strategy. Whatever the approach, the pathologist is directly implicated as Lynch syndrome harbors specific histological aspects that can help to its identification, but also as pre-screening tests are directly realized on tumor-tissue.

A case of Muir-Torre syndrome associated with mucinous hepatic cholangiocarcinoma and a novel germline mutation of the MSH2 gene.

Muir-Torre syndrome (MTS) is a rare cancer-predisposing syndrome that is autosomal dominantly inherited and characterized by the development of sebaceous skin lesions (adenomas, epitheliomas, basaliomas and carcinomas). These lesions are typically associated with tumors that belong to the spectrum of hereditary nonpolyposis colorectal cancer (HNPCC) (i.e., tumors of the colorectum, endometrium, stomach or ovary). Biliary malignancy in association with MTS has only rarely been reported. We report a case of Muir-Torre syndrome associated with intrahepatic cholangiocarcinoma, a location not previously described, and associated with a novel missense mutation of the MSH2 gene (c.2026T > C), predicted to disrupt the function of the gene.

Disease severity and genetic pathways in attenuated familial adenomatous polyposis vary greatly but depend on the site of the germline mutation.

BACKGROUND: Attenuated familial adenomatous polyposis (AFAP) is associated with germline mutations in the 5', 3', and exon 9 of the adenomatous polyposis coli (APC) gene. These mutations probably encode a limited amount of functional APC protein. METHODS AND RESULTS: We found that colonic polyp number varied greatly among AFAP patients but members of the same family tended to have more similar disease severity. 5' Mutants generally had more polyps than other patients. We analysed somatic APC mutations/loss of heterozygosity (LOH) in 235 tumours from 35 patients (16 families) with a variety of AFAP associated germline mutations. In common with two previous studies of individual kindreds, we found biallelic changes ("third hits") in some polyps. We found that the "third hit" probably initiated tumorigenesis. Somatic mutation spectra were similar in 5' and 3' mutant patients, often resembling classical FAP. In exon 9 mutants, in contrast, "third hits" were more common. Most "third hits" left three 20 amino acid repeats (20AARs) on the germline mutant APC allele, with LOH (or proximal somatic mutation) of the wild-type allele; but some polyps had loss of the germline mutant with mutation leaving one 20AAR on the wild-type allele. CONCLUSIONS: We propose that mutations, such as nt4661insA, that leave three 20AARs are preferentially selected in cis with some AFAP mutations because the residual protein function is near optimal for tumorigenesis. Not all AFAP polyps appear to need "three hits" however. AFAP is phenotypically and genetically heterogeneous. In addition to effects of different germline mutations, modifier genes may be acting on the AFAP phenotype, perhaps influencing the quantity of functional protein produced by the germline mutant allele.

N-acetyltransferase 2 influences cancer prevalence in hMLH1/hMSH2 mutation carriers.

Hereditary nonpolyposis colorectal cancer (HNPCC), an inherited cancer predisposition syndrome, has been associated with germline mutations in DNA mismatch repair (MMR) genes. Because a deficiency in MMR does not predict a specific cancer phenotype, modifying genes may account in part for the variation in disease expression. We determined the N-acetyltransferase 2 (NAT2) genotype in 26 unaffected and 52 cancer-affected hMLH1/hMSH2 mutation carriers coming from 21 Swiss HNPCC families. Slow acetylators were found to be significantly (P < 0.03) more prevalent in the group of affected mutation carriers. Our results suggest a protective effect of the NAT2 rapid acetylator phenotype, an observation that could have implications for genetic counseling and management of MMR gene mutation carriers.

[Colorectal cancer: a risk-adapted screening and the role of the physician in the prevention of this cancer]. / Cancer colorectal: dépistage adapté au risque et rôle du médecin traitant dans la prévention de ce cancer.

The benefit of colorectal cancer screening in the average-risk population, as well as in the presence of high risk genetic predispositions, has been validated by a significant reduction of the mortality associated with the disease. Several screening options are recognized and compliance with these measures remains a public health problem. The physician plays a key role in the promotion of the colorectal cancer screening. Collecting a precise family history is crucial for the identification of individuals at high risk. Validated clinical criteria are helpful for the identification of individuals with a genetic predisposition to colorectal cancer. Molecular screening for the main colorectal cancer predisposing genes should now be integrated in the clinical management of these patients and their families.

A genetic basis for the inviability of hybrids between sibling species of Drosophila.

A mutation of Drosophila melanogaster whose only known effect is the rescue of otherwise lethal interspecific hybrids has been characterized. This mutation, Hmr, maps to 1-31.84 (9D1-9E4). Hmr may be the consequence of a P element insertion. It rescues hybrid males from the cross of D. melanogaster females to males of its three sibling species, D. simulans, D. mauritiana and D. sechellia. This rescue is recessive, since hybrid males that carry both Hmr and a duplication expected to be Hmr+ are not rescued. Hmr also rescues the otherwise inviable female hybrids from the cross of compound-X D. melanogaster females to males of its sibling species. This rescue is also recessive, since a compound-X heterozygous for Hmr does not rescue. Another mutation, discovered on the In(1)AB chromosome of D. melanogaster, is also found to rescue normally inviable species hybrids: unlike Hmr, however, In(1)AB rescues hybrid females from the cross of In(1)AB/Y males to sibling females, as well as hybrid males from the cross of In(1)AB females to sibling males. These data are interpreted on the basis of a model for the genetic basis of hybrid inviability of complementary genes.

An MLH1 haplotype is over-represented on chromosomes carrying an HNPCC predisposing mutation in MLH1.

BACKGROUND: The mismatch repair gene, MLH1, appears to occur as two main haplotypes at least in white populations. These are referred to as A and G types with reference to the A/G polymorphism at IVS14-19. On the basis of preliminary experimental data, we hypothesised that deviations from the expected frequency of these two haplotypes could exist in carriers of disease associated MLH1 germline mutations. METHODS: We assembled a series (n=119) of germline MLH1 mutation carriers in whom phase between the haplotype and the mutation had been conclusively established. Controls, without cancer, were obtained from each contributing centre. Cases and controls were genotyped for the polymorphism in IVS14. RESULTS: Overall, 66 of 119 MLH1 mutations occurred on a G haplotype (55.5%), compared with 315 G haplotypes on 804 control chromosomes (39.2%, p=0.001). The odds ratio (OR) of a mutation occurring on a G rather than an A haplotype was 1.93 (95% CI 1.29 to 2.91). When we compared the haplotype frequencies in mutation bearing chromosomes carried by people of different nationalities with those seen in pooled controls, all groups showed a ratio of A/G haplotypes that was skewed towards G, except the Dutch group. On further analysis of the type of each mutation, it was notable that, compared with control frequencies, deletion and substitution mutations were preferentially represented on the G haplotype (p=0.003 and 0.005, respectively). CONCLUSION: We have found that disease associated mutations in MLH1 appear to occur more often on one of only two known ancient haplotypes. The underlying reason for this observation is obscure, but it is tempting to suggest a possible role of either distant regulatory sequences or of chromatin structure influencing access to DNA sequence. Alternatively, differential behaviour of otherwise similar haplotypes should be considered as prime areas for further study.

Molecular and clinical characteristics in 32 families affected with familial adenomatous polyposis.

Germ-line mutations in the 5' half of the Adenomatous Polyposis Coli (APC) gene are found in about 80% of the patients affected with familial adenomatous polyposis (FAP). The vast majority of these are nonsense or frameshift mutations which result in the loss of the carboxyl terminus of the APC protein. Using an in vivo assay in yeast, we have identified pathogenic germ-line mutations in 26 of 32 (81%) unrelated Swiss families affected with FAP. Nine mutations were novel and eight families were shown to harbor two recurrent mutations. Correlations were attempted between the location of APC germ-line mutations and clinical manifestations of the disease.

Acute and chronic noradrenergic regulation of neurotrophin messenger RNA expression in rat hippocampus: evidence from lesions and organotypic cultures.

Noradrenergic neurons from the locus coeruleus innervate several brain regions, such as hippocampus and cortex. The hippocampus exhibits the highest concentration of the neurotrophins nerve growth factor, brain-derived neurotrophic factor and neurotrophin-3 in the brain. To study the role of the noradrenergic system in the chronic regulation of neurotrophin messenger RNA expression, chemical [N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine, 6-hydroxydopamine] and mechanical (knife-cut axotomy) lesions were performed, in the rat, and neurotrophin messenger RNAs analysed after 14 and 35 days. The intensity of the lesion was verified by characterization of the noradrenergic system using immunohistochemistry and in situ hybridization for dopamine-beta-hydroxylase and the measurement of noradrenaline tissue levels. To study the acute regulation, hippocampal organotypic slice cultures were prepared and neurotrophin messenger RNAs analysed after incubation in different concentrations of noradrenaline. We report that the noradrenergic N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine depletion significantly increased nerve growth factor and brain-derived neurotrophic factor messenger RNAs but not neurotrophin-3 messenger RNA in hippocampal areas 35 days after the lesion, while the knife-cut axotomy had a less pronounced effect and the 6-hydroxydopamine lesion did not change the neurotrophins. When incubating the organotypic hippocampal cultures with different concentrations of noradrenaline, nerve growth factor and brain-derived neurotrophic factor messenger RNAs but not neurotrophin-3 messenger RNA were significantly reduced in the dentate gyrus. We conclude that nerve growth factor and brain-derived neurotrophic factor but not neurotrophin-3 expression are inhibited by noradrenaline, arising from the locus coeruleus.

Twenty-five years' experience with the arterial switch operation.

OBJECTIVE: The arterial switch operation was introduced in 1976 to correct transposition of the great arteries and has since replaced atrial palliation. This study examines the long-term outcomes of the arterial switch operation. METHODS: Included in the study were 195 patients who underwent the arterial switch operation from 1977 through June 2000. Patients were evaluated for functional class, pulmonary stenosis, left ventricular function, arrhythmias, aortic sequelae, and coronary disease. RESULTS: Overall perioperative mortality was 15%, but rates dropped in the last 5 years to 4% for complex transposition and 0% for simple transposition. Of 151 survivors, 2 died late; 1 died of persisting pulmonary hypertension and 1 died of ventricular fibrillation after coronary pathologic changes. At last follow-up, a total of 145 patients were in New York Heart Association functional class I and 4 patients were in class II. The most frequent complication was pulmonary stenosis, necessitating 45 reinterventions in 26 patients. Left ventricular dysfunction was noted in 5 patients. Arrhythmias were seen in 5 patients: 2 patients had ventricular fibrillation (1 died and 1 required a defibrillator implantation), 1 had sick sinus syndrome, 1 had atrial flutter, and 1 had a single attack of supraventricular tachycardia. Aortic valve incompetence was absent or trivial in 146 patients, 3 had mild incompetence, 1 had moderate incompetence, and 1 had severe incompetence. Coronary sequelae were found in 5 of the 61 patients who underwent angiography. CONCLUSION: Long-term clinical outcome of the arterial switch operation is good, and perioperative mortality is now low. Morbidity is dominated by pulmonary stenosis and coronary artery disease, with the potential for lethal arrhythmias.

A mutagenic PCR identifies isolates of Borrelia garinii responsible for Lyme borreliosis.

Borrelia garinii is one of the three major Borreliae responsible for Lyme borreliosis in Europe. We have characterized a protein of B. garinii (VS102) and a genomic fragment from the gene encoding this protein was cloned. The DNA sequence of the fragment showed high homology with a known gene of B. burgdorferi sensu stricto. The protein encoded by this gene in B. burgdorferi sensu stricto is a phosphocarrier protein (histidine-containing protein). A mutation T to G polymorphism at codon 57 was found to be specific to B. garinii. A PCR-based approach that allows the rapid detection of this mutation made it possible to specifically discriminate B. garinii from other B. burgdorferi genospecies with high sensitivity and specificity.

Catastrophic transcatheter baffle fenestration for failing Fontan physiology.

Transcatheter fenestration and balloon dilation of an atrial baffle created from native atrial tissue was attempted in a 15-year-old girl with failing Fontan physiology and protein-losing enteropathy. After transseptal puncture, initial dilations with a 10-mm and 12-mm diameter balloon resulted in an inadequate fenestration, with no significant decrease of right atrial pressure or systemic arterial saturation. Dilation of the fenestration with a 16-mm-diameter balloon produced a tear of the atrial septum and subsequent death. Balloon dilation of native atrial tissue may result in uncontrolled tears of the atrial septum.

Aneurysmal pericardial patch producing right ventricular inflow obstruction.

A 2-month-old infant presented with acute onset of heart failure, having previously undergone anatomical repair of transposition of the great arteries and ventricular septal defect (VSD). Echocardiography demonstrated aneurysmal dilation of the native pericardial patch used for VSD closure, resulting in right ventricular inflow obstruction. The pericardial patch was excised, and the VSD closed using a GoreTex patch.

Sustained high pressure double balloon angioplasty of calcified conduits.

OBJECTIVE: To assess the efficacy of prolonged high pressure angioplasty for dilatation of calcified and stenotic cardiac conduits in children. DESIGN: A prospective study of consecutive patients presenting with calcified and stenotic conduits. SETTING: Two tertiary paediatric cardiology departments. METHODS: Sustained (up to five minutes), high pressure (up to 18 atmospheres), double balloon angioplasty was performed in six calcified and stenotic cardiac conduits (five consecutive patients, three male, two female, age 4 to 17 years). Four patients had right ventricle to pulmonary artery (RV-PA) conduits, and one had two venous conduits in a Fontan circulation. RESULTS: Marked reductions in right ventricle to pulmonary artery gradients, from a median (range) of 48 (40 to 62) mm Hg to 11 (5 to 16) mm Hg, and in right ventricle to femoral artery pressure ratios, from a median of 0.8 (0.72 to 0.86) to 0.4 (0.33 to 0.44), were achieved for all RV-PA conduits. All five patients had sustained clinical improvement at follow up (median follow up 12 months) and none has required reintervention or surgery. CONCLUSIONS: Prolonged high pressure double balloon angioplasty may have a role in prolonging the interval between conduit replacements in a subset of patients with complex heart defects.

Junctional ectopic tachycardia evolving into complete heart block.

Transition from congenital junctional ectopic tachycardia to complete AV block was observed in an 8 month old girl, over a 36 hour period, during initial hospital admission. Two years later she had evidence of a rapidly increasing left ventricular end diastolic diameter, associated with lowest heart rates during sleep of < 30 beats/min. A transvenous permanent pacemaker was therefore implanted. This finding supports the idea that a pathological process in the area of the AV junction, initially presenting as junctional ectopic tachycardia may later extend to sudden complete atrioventricular block.

Lung perfusion studies after detachable coil occlusion of persistent arterial duct.

OBJECTIVE: To evaluate relative lung perfusion following complete occlusion of persistent arterial duct with detachable Cook coils. METHODS: Ductal occlusion using detachable coils was performed in 35 patients (median age 3.9 years, range 0.5 to 16; 32 native ducts, three patients with previous devices). If the duct could be crossed with a 0.035 inch guidewire and a 4 F catheter after coil implantation, a further coil was implanted. Between one and seven coils were used (median two). RESULTS: Complete ductal occlusion was confirmed by echocardiography 24 hours after the procedure in all patients. Lung perfusion scans were performed three months after the procedure in 33 of 35 patients (two older patients with a single coil each did not attend). Decreased perfusion to the left lung (defined as < 40% of total lung flow) was observed in only one patient, who had previously had a 17 mm Rashkind umbrella implanted. There was no correlation between left lung perfusion and peak left pulmonary artery Doppler velocities (r = 0.27 and p = 0.125 for the entire group; r = 0.29 and p = 0.124 after excluding patients with previous devices). CONCLUSIONS: Coil occlusion is effective in achieving complete closure of the duct. An aggressive approach using multiple coils did not compromise perfusion to the left lung.

Fate of the aortic root after arterial switch operation.

OBJECTIVE: Concerns have been voiced about possible dilation and insufficiency of the neo-aortic valve after the arterial switch operation (ASO). AIMS: To determine growth of the neo-aortic valve and the aortic anastomosis after ASO and the prevalence of insufficiency or stenosis. PATIENTS AND METHODS: Since 1977, 144 consecutive patients (pts) underwent ASO for transposition of the great arteries (TGA). Median follow-up was 8.65 years (0.1--22.5 years). Simple TGA was present in 97 pts and 47 had TGA with ventricular septal defect (VSD). Detailed echocardiography included measurements of aortic diameter at four levels. The 608 measurements were compared with published normal values. RESULTS: The mean aortic valve z-score was 1.5, without significant change with age (P=0.75). Under 4 months, mean valve z-score was 0.63+/-2.20, between 5 and 12 months 2.56+/-2.30 (P<0.0001). Gradual growth occurs thereafter. The aortic sinus follows an identical growth pattern. The aorta at the anastomosis, is initially smaller than normal (z-score -0.64). After 4 months the z-score is 0.83, followed by continued growth of 0.1 z-score per year. At the last visit, the aortic valve z-score was above 2 in 51 patients, between -2 and 2 in 72 and less than -2 in six patients, none of whom had a flow velocity above 2 m/s. z-score of patients with VSD remained above those without VSD (P<0.0001). Aortic insufficiency was grade 2/4 in three patients, grade 3/4 in one and grade 4/4 in one. No patient developed aortic stenosis. CONCLUSION: After ASO the neo-aortic valve and sinus are larger than normal, representing the natural size difference in the prenatal situation and influence of associated cardiac malformations. In the first year of life, rapid dilatation of the new aorta is observed, followed by growth towards normalization of the valve and sinus size. Stenosis at the anastomosis was not observed. Aortic dilatation by itself is rarely associated with significant insufficiency.

Late re-interventions following arterial switch operations in transposition of the great arteries. Incidence and surgical treatment of postoperative pulmonary stenosis.

Seventy-six patients were studied after arterial switch operation (ASO) between May 1977 and February 1992. Pulmonary artery reconstruction was initially performed by: conduit interposition in 5 patients, direct main pulmonary artery anastomosis and button patches in 60 patients, and pantaloon-like patch repair in 11 patients. Pulmonary stenosis developed in 17 patients (22%), requiring a total of 26 late re-interventions. Re-intervention was required in four out of five patients operated with pulmonary artery conduits, 11 out of 60 with a button patch repair and 2 out of 11 following pantaloon-type repair. In this series pulmonary artery stenosis (PS) involving the pulmonary valve occurred in 9/17 patients. Involvement of the pulmonary valve was related to the technique of pulmonary artery reconstruction. In these patients surgery is necessary. Balloon angioplasty can be a valuable tool when the stenosis is more distal. The incidence of PS was not influenced by the type of reconstruction or the use of Lecompte's maneuver.

Influence of coronary anatomy and reimplantation on the long-term outcome of the arterial switch.

BACKGROUND: Abnormal coronary artery anatomy is reported to have a significant influence on the outcome of the arterial switch operation. This study examines the impact of coronary anatomy and the occurrence of late coronary obstruction on left ventricular (LV) function and long-term outcome. METHODS: Coronary artery anatomy, of 170 patients after arterial switch operation (1977-1999), was determined based on operative reports and pre-operative aortograms. Current status was evaluated using ECGs, echocardiograms, scintigraphy, and post-operative coronary angiograms. RESULTS: In 133/170 patients, coronary artery anatomy consisted of an anterior descending (LAD) and circumflex artery (Cx) from the left sinus and the right coronary artery (RCA) from the right or posterior sinus. The left coronary had an intramural initial course in two of these patients. Fifteen patients had the LAD from the left and Cx and RCA from the right sinus; eight had LAD and RCA from one sinus and Cx from the other; four had single ostium; and three had three separate ostia. Four patients had complex patterns and four patients had a supra commissural coronary. To date, follow-up angiography was performed in 59 patients. Surgical coronary sequellae were found in five patients. Two patients had an occluded left ostium. Initially, they were asymptomatic but showed polymorphic ventricular extrasystoles on ECG and moderate LV dysfunction with large irreversible perfusion defects on scintigraphy. Both patients developed ventricular fibrillation at the age of 14 years. One patient did not survive. The other patient required implantation of a defibrillator. One patient has an occluded RCA, one patient has stenosis of the right ostium and one patient has multiple tortuous collaterals without obstruction of a major branch. In the latter three patients, coronary sequellae were not suspected on ECG, echo, or scintigraphy and were only found on follow-up angiography. Retrograde collateral flow was noted in all three occluded coronaries. LV dysfunction, with normal coronaries, was noted in three patients. All, of these patients, had peri-operative ischaemia suggesting failure of myocardial protection. Two are now asymptomatic with mild LV dysfunction. One patient continues to have severe myocardial dysfunction and secondary aortic insufficiency. A Ross-like procedure was performed placing the original aortic valve in the neo-aortic root. Coronary artery anatomy did not influence early survival or late coronary sequellae. CONCLUSION: Abnormal coronary anatomy was not a determinant of outcome in our study. Surgical coronary obstruction is independent of original anatomy. It can be almost silent and is potentially fatal. Follow-up angiography must be considered in all patients after the arterial switch operation.