Segregation analysis of NIDDM in Caucasian families

Non-insulin-dependent diabetes mellitus (NIDDM) has a substantial genetic component, but the mode of inheritance and the molecular basis are unknown. We have undertaken segregation analysis of NIDDM after studying 247 subjects in 59 Caucasian nuclear pedigrees ascertained without regard to family history of the disorder. The analyses were performed using POINTER and COMDS, which are computer programs which apply statistical models to the data. POINTER analysis was performed defining the phenotype as a presence or absence of hyperglycaemia. Among single locus hypothesis, the analyses rejected a recessive model and favoured a dominant model, but could not statistically show that this fitted better than a mixed model (a single locus against a polygenic background) or a polygenic model. COMDS analysis assumed a continuum of hyperglycaemia from normality to NIDDM, classified family members into a series of diathesis classes with increasing plasma glucose levels and compared the distribution with that found by screening the normal population. This analysis improved the likelihood of a dominant single locus model and suggested a gene frequency of 7.4%. It raised the possibility of a second locus, but cannot identify or exclude a polygenic model. In conclusion, two types of segregation analyses rejected a recessive model and favoured a dominant model of inheritance, although they could not statistically show that this fitted better than the polygenic model. The results raised the possibility of a common dominant gene with incomplete penetrance, but genetic analysis of NIDDM needs to take into account the likelihood of polygenic inheritance with genetic heterogeneity.     

The major locus for multifactorial nonsyndromic cleft lip maps to mouse chromosome 11

Cleft lip with or without cleft palate, CL(P), a common human birth defect, has a genetically complex etiology. An animal model with a similarly complex genetic basis is established in the A/WySn mouse strain, in which 20% of newborns have CL(P). Using a newly created congenic strain, AEJ.A, and SSLP markers, we have mapped a major CL(P)-causing gene derived from the A/WySn strain. This locus, here named clf1 (cleft lip) maps to Chromosome (Chr) 11 to a region having linkage homology with human 17q21-24, supporting reports of association of human CL(P) with the retinoic acid receptor alpha (RARA) locus.     

Nonsyndromic cleft lip with or without cleft palate: evidence of linkage to BCL3 in 17 multigenerational families

Nonsyndromic cleft lip with or without cleft palate (CL/P) is a common craniofacial developmental defect. Recent segregation analyses have suggested that major genes play a role in the etiology of CL/P. Linkage to 22 candidate genes was tested in 11 multigenerational families with CL/P, and 21 of these candidates were excluded. APOC2, 19q13.1, which is linked to the proto-oncogene BCL3, gave suggestive evidence for linkage to CL/P. The study was expanded to include a total of 39 multigenerational CL/P families. Linkage was tested in all families, using an anonymous marker, D19S178, and intragenic markers in BCL3 and APOC2. Linkage was tested under two models, autosomal dominant with reduced penetrance and affecteds only. Homogeneity testing on the two-point data gave evidence of heterogeneity at APOC2 under the affecteds-only model. Both models showed evidence of heterogeneity, with 43% of families linked at zero recombination to BCL3 when marker data from BCL3 and APOC2 were included. A maximum multipoint LOD score of 7.00 at BCL3 was found among the 17 families that had posterior probabilities > = 50% in favor of linkage. The transmission disequilibrium test provided additional evidence for linkage with the 3 allele of BCL3 more often transmitted to affected children. These results suggest that BCL3, or a nearby gene, plays a role in the etiology of CL/P in some families.     

Genetic factors study in family aggregation of schizophrenia in Santiago, Chile

BACKGROUND: Genetic epidemiological studies indicate that genetic factors contribute to a familial aggregation of schizophrenia. The form of inheritance has not been elucidated but most studies have been done in Caucasian populations. AIM: To study the form of inheritance of schizophrenia in an urban population of Santiago, Chile, containing an admixture of Spanish origin individuals with Southamerican aborigines. SUBJECTS AND METHODS: Forty four randomly selected schizophrenic probands, 22 female, aged 28 to 48 years old, were studied. From them, an extensive genealogical reconstitution was performed. Probands and relatives were interviewed using the structured interview CIDI and DSM-III-R check-list. Schizophrenia was diagnosed using DSM-III-R criteria. Complex segregation analysis was done using Pointer program. RESULTS: The hypothesis of a multifactorial inheritance, without the participation of major genes, could not be rejected. Likewise, the major dominant and co-dominant gene forms of transmission could not be rejected. CONCLUSIONS: Our results show the participation of a major dominant locus and a multifactorial component in the inheritance of schizophrenia, as has been reported elsewhere.     

Association of MSX1 and TGFB3 with nonsyndromic clefting in humans

Nonsyndromic cleft lip with or without cleft palate (CL/P) and nonsyndromic cleft palate only (CPO) are common congenital anomalies with significant medical, psychological, social, and economic ramifications. Both CL/P and CPO are examples of complex genetic traits. There exists sufficient evidence to hypothesize that disease loci for CL/P and CPO can be identified by a candidate-gene linkage-disequilibrium (LD) strategy. Candidate genes for clefting, including TGFA, BCL3, DLX2, MSX1, and TGFB3, were screened for LD with either CL/P or CPO in a predominantly Caucasian population, with both case-control- and nuclear-family-based approaches. Previously reported LD for TGFA with both CL/P and CPO could not be confirmed, except in CL/P patients with a positive family history. Also, in contrast to previous studies, no LD was found between BCL3 and either CL/P or CPO. Significant LD was found between CL/P and both MSX1 and TGFB3 and between CPO and MSX1, suggesting that these genes are involved in the pathogenesis of clefting. In addition, a mutation search in the genes DLX2, MSX1, and TGFB3 was performed in 69 CPO patients and in a subset of the CL/P patients. No common mutations were found in the coding regions of these genes; however, several rare variants of MSX1 and TGFB3 were found that may alter the latters' normal function. These results form the basis for future research, including (a) mutation searches in the MSX1 and TGFB3 genes in Caucasian CL/P patients and (b) extension of the search for MSX1 mutations in CPO patients to the noncoding regions.     

A new syndrome of cleft palate associated with coloboma, hypospadias, deafness, short stature, and radial synostosis

A new syndrome characterized by cleft palate, coloboma, hypospadias, deafness, short stature, and radial synostosis has been described. The family history suggests either an autosomal dominant mode of inheritance with limited expression in females or X-linkage. Other syndromes with similar phenotypes and modes of inheritance are discussed. The need for accurate and complete family histories in cases involving cleft palate and cleft lip/palate is discussed in relation to genetic counselling and recurrent risk estimates.     

Segregation analysis of epithelial ovarian cancer in Finland

Epithelial ovarian cancer is known to aggregate in families. The dominantly inherited ovarian cancer predisposing genes, BRCA1, BRCA2 and genes involved in the hereditary non-polyposis colorectal cancer (HNPCC) syndrome, have recently been identified. However, in the majority of families with more than one case of ovarian cancer, dominant inheritance cannot be recognized. We investigated familial clustering of epithelial ovarian cancer in a population-based sample of 663 Finnish ovarian cancer patients. A segregation analysis with the POINTER software was conducted on the 937 nuclear families from these 663 pedigrees. The major gene model was favoured, and the sporadic and multifactorial models were strongly rejected. In the studied population, the best fitting model was a recessive mode of inheritance, and 8% of ovarian cancer patients were estimated to be homozygous for the deleterious genotype. This evidence for recessively inherited ovarian cancer predisposition should be interpreted cautiously, as the analysis is subject to certain errors, which are discussed in the article. Results of this analysis, however, strongly emphasize the role of genetic factors in all familial aggregation of epithelial ovarian cancer.     

Segregation analysis of complex phenotypes: an application to schizophrenia and auditory P300 latency

Traditional models of the genetic transmission of human diseases have often assumed that the phenotype is a simple dichotomous trait, which is unrealistic for many psychiatric conditions, and may result in loss of valuable information. We describe a new model for complex phenotypes, implemented in the program COMDS, which subclassifies normal and affected individuals into polychotomies correlated with the underlying genetic liability to the disorder. The model is applied to 18 Scottish pedigrees ascertained for schizophrenia, in which auditory P300 latency had been measured as a possible correlate of the genetic predisposition to schizophrenia. The results suggest that there may be a major locus for schizophrenia, but that there are also other familial determinants, possibly a second modifier locus. In addition, the results indicate that auditory P300 latency may be a useful measure of the genetic predisposition to schizophrenia among asymptomatic relatives, although the relationship between P300 latency and the degree of genetic predisposition in clinical cases was not significant, presumably because other factors are operating on P300 latency. Because of the possible selection biases in this sample, there is a need to replicate these findings in systematically ascertained pedigrees.     

Deficient and delayed primary palatal fusion and mesenchymal bridge formation in cleft lip-liable strains of mice

During mammalian primary palate formation, the facial prominences enlarge around the nasal pit, fuse and then merge to give rise to the tissue of the upper lip and premaxillary region. The mechanisms involved in successful primary palate formation and how they are affected in the cleft lip genotype remain poorly understood. The purpose of this study was to compare morphometrically internal development and growth of the primary palate in five different strains of mice. Two of the strains, BALB/cByJ, and C57BL/6J, have normal primary palate development, and three of the strains, A/J, A/WySn, and CL/Fr, have stable frequencies of cleft lip associated with genotype. In the present study, frequencies of 4, 23, and 24%, respectively, were observed on day 13. For palatal growth analysis, embryos were collected on days 10 and 11, staged by number of tail somites (TS), and the heads were photographed and serially sectioned for measurement of primary palate components. The heights of the epithelial seam and the mesenchyme bridge between the facial prominences were measured on serial sections and areas of contact were calculated. The position or depth of the maxillary prominence was determined from the number of frontal sections from its tip to the rostral end of the nasal fin. Analysis of measurements showed that in cleft lip strains enlargement of the epithelial seam and replacement of epithelia by a mesenchymal bridge were both delayed relative to somite stages. Measurements from day 11 embryos with complete failure of contact were excluded from the growth analyses. The mesenchymal bridge formed at 12--13 TS in noncleft strains, 14 TS in the A/J strains with higher cleft lip frequency, and 15--17 TS in A/WySn and CL/Fr strains with higher cleft lip frequency. Forward growth of the maxillary prominence was highly correlated with the primary palate measurements and mesenchymal bridge formation in all strains. In both cleft and noncleft strains, the primitive choanae open at 18--20 TS and the medial nasal region narrows with advancing embryonic development. As a result, cleft lip-liable strains have a narrower window in development in which a robust mesenchymal bridge must form, thus increasing the liability to cleft lip.     

Convergence of nociceptive and non-nociceptive inputs onto spinal reflex pathways to the tibialis anterior muscle in humans

To investigate whether the familial clustering of cutaneous melanoma is consistent with Mendelian inheritance of a major autosomal gene, maximum likelihood segregation analyses were performed in a population-based sample of 1,912 families ascertained through a proband with melanoma diagnosed in Queensland between 1982 and 1990. Analyses were performed with the S.A.G.E. statistical package, using the REGTL program for a binary trait with a variable age of onset. We sought medical confirmation for all family members reported to have had melanoma, and only medically verified cases among relatives were included in the analyses. The hypothesis of codominant Mendelian inheritance gave a significantly better fit to the data than either dominant or recessive Mendelian inheritance, or environmental transmission. Overall, both Mendelian inheritance of a single major gene, and purely environmental transmission were rejected (P < 0.001). In both the single major gene and environmental models, there was strong evidence of familial dependence in melanoma occurrence (P < 0.001). These results are consistent with reported genetic heterogeneity in melanoma inheritance and suggest that other familial factors, such as pigmentation, skin type, and sun exposure habits, may play an important role in the familial clustering of melanoma.     

Nonsyndromic cleft lip and palate: no evidence of linkage to HLA or factor 13A

Nonsyndromic cleft lip with or without cleft palate (CLP) is a common craniofacial anomaly, the etiology of which is not known. Population studies have shown that a large proportion of cases occur sporadically. Recently, segregation analyses applied to CLP families have demonstrated that an autosomal dominant/codominant gene(s) may cause clefting in cases. Associations of autosomal dominant CLP and nonsyndromic cleft palate (CP) with HLA and F13A genes on chromosome 6p have been suggested previously. Linkage to these two areas on chromosome 6p were tested in 12 autosomal dominant families with CLP. With a LOD score of -2 or less for exclusion, no evidence of linkage was found to four chromosome 6p markers. Multipoint analysis showed no evidence of a clefting locus in this region spanning 54 cM on chromosome 6p in these CLP families.     

Segregation analysis of Parkinson disease

Parkinson disease (PD) is a prevalent movement disorder of unknown cause whose incidence rises with increasing age. Nearly 20% of PD is familial, a small subset of which exhibits autosomal dominant transmission. However, in most families, the inheritance is not clear. To determine the most likely mode of inheritance of PD, we performed complex segregation analyses using kindreds of 136 PD patients randomly ascertained from a clinic population. The hypotheses of a nontransmissible environmental factor, no major gene or type (sporadic), and all Mendelian inheritance (dominant, recessive, additive, decreasing) were rejected (P <0.001). Familial clustering of PD in this data set is best explained by a rare familial factor which a) is transmitted in a nonMendelian fashion, and b) influences the age at onset of PD. If confirmed, our results have immediate implications in gene-mapping studies which often search for genes that behave in a Mendelian fashion that affect susceptibility rather than age at onset and long term implications in understanding the pathogenesis of PD.     

Major locus influencing plasma APO-A1 levels also controls plasma HDL3-C concentrations

Elevated plasma levels of apolipoprotein A1 (APO-A1) and high-density lipoprotein cholesterol (HDL-C) are important protective factors for atherosclerosis and coronary heart disease. Using the data on plasma concentrations of APO-A1, and HDL-C particles HDL2-C and HDL3-C in 970 Israeli individuals belonging to 228 pedigrees, we tested the hypothesis that a major locus influencing interindividual variation in APO-A1 levels also controls interindividual variation in HDL3-C and HDL2-C levels. Univariate and bivariate complex segregation analyses, as implemented in two statistical packages (MAN-3 and PAP-4.0) were applied to test the hypothesis. The results of the analysis clearly indicated the possibility of major gene involvement in the determination of plasma concentration variation of each of the 3 study variables. The results provide strong evidence in support of our hypothesis that HDL3-C genetic variation fully depends on the APO-A1 major locus. In particular, environmental and sporadic models were strongly rejected (P < 0.001) in bivariate analysis. The hypothesis of no pleiotropic effect of the putative APO-A1 locus on HDL3-C transmission was also unequivocally rejected (P < 0.001), while the bivariate Mendelian model was accepted (P > 0.05). The results of bivariate analysis of APO-A1 effect on HDL2-C were not clear. They indicated the possibility of the existence of slight genetic covariation between the two variables, and as yet we were unable to decipher the mode of covariation with the applied models.     

Two sibs with cleft palate, ankyloblepharon, alveolar synechiae, and ectodermal defects: a new recessive syndrome?

Hay and Wells in 1976 reported seven patients from four families who had an inherited condition of which the main features were ankyloblepharon, ectodermal defects, and cleft lip and palate. The inheritance pattern was determined to be autosomal dominant. This condition is known as AEC syndrome or Hay-Wells syndrome. We report a family with two sibs showing some of these features and congenital adhesions between the upper and lower jaws (alveolar synechiae). There seems to be a recessive pattern of inheritance as neither of the parents has any features of the syndrome. This could be described as a recessive form of Hay-Wells syndrome with additional features or be named as a new syndrome.     

Prospective evaluation of morbidity associated with iliac crest harvest for alveolar cleft grafting

PURPOSE: This study prospectively evaluated the morbidity associated with iliac crest bone harvest when performed for alveolar cleft grafting. PATIENTS AND METHODS: Twenty-two consecutive patients who underwent an alveolar cleft graft with iliac crest bone harvest were evaluated. The estimated blood loss, length of hip incision, and volume of bone that was harvested were recorded. The duration of time until postoperative ambulation and the length of hospitalization were measured. RESULTS: All patients tolerated the iliac harvest without major complication, and the volume of bone was sufficient in all but one case. Postoperatively, ambulation occurred at an average of 3 hours 18 minutes. Twenty-one patients were discharged the day after surgery; one patient had the surgery performed as an outpatient. CONCLUSIONS: Harvesting cancellous bone from the iliac crest does not result in delayed ambulation or prolonged hospitalization. The morbidity that has been reported to occur with iliac crest bone harvest was not consistent with the results of this study.     

Review: the Michigan cleft twin study

The combined effects of clefting of the lip and/or palate and of their surgical repair have been examined for a cross-sectional sample of 20 MZ and 25 DZ like-sexed twins discordant for clefting, in the age range of 4 to 17 years. The findings of four studies published since 1975 on that sample are explored for the primary, contiguous and pleiotropic effects of clefting. The primary effects on facial structures of repaired cleft lip appear to be minimal. However, for twins with repaired cleft of the palate (with or without cleft of the lip), the maxilla was both deficient antero-posteriorly and was positioned more posteriorly than in their non-cleft co-twins. The maxillary first molars were usually slightly less erupted in the cleft twins than in the non-cleft twins. The cleft palate only twins had larger cranial base angles than their non-cleft co-twins. A contiguous effect of the posteriorly positioned maxilla was a mandibular rotation downward and backward in the cleft palate and bilateral cleft lip and palate groups but not in the unilateral cleft lip and palate group. The slightly larger cranial base angles found for cleft palate only, although contiguous in location, are more likely pleiotropic effect. The pleiotropic effects include a deficit in height and weight for cleft subjects which appears only after puberty. Although the teeth of the cleft twins tended to be smaller than those of the non-cleft twins, the amount was not clinically significant.     

Antineurofilament and antiretinal antibodies in AIDS patients with cytomegalovirus retinitis

Approximately 5% of children with neural tube defects (NTDs) have a congenital heart defect and/or cleft lip and palate. The cause of isolated meningomyelocele, congenital heart defects, or cleft lip and palate has been largely thought to be multifactorial. However, chromosomal, teratogenic, and single gene causes of combinations of NTDs with congenital heart defects and/or cleft lip and palate have been reported. We report on 3 patients with meningomyelocele, congenital heart defects, and 22q11 deletions. Two of the children had the clinical diagnosis of velo-cardio-facial syndrome (VCFS); both also have bifid uvula. The third child had DiGeorge sequence (DGS). The association of NTDs with 22q11 deletions has not been reported previously. An accurate diagnosis of the 22q11 deletion is critical as this micro-deletion and its associated clinical problems is transmitted as an autosomal dominant trait due to the inheritance of the deletion-bearing chromosome. We recommend that all children with NTDs and congenital heart defects, with or without cleft palate, have cytogenetic and molecular studies performed to detect 22q11 deletions.     

Alveolar bone grafting in unilateral complete cleft lip and palate patients

Autogenous bone graft of an alveolar cleft area has the following advantages: (1) assistance in the closure of buccoalveolar oronasal fistula; (2) provision of bony support for unerupted teeth and teeth adjacent to the cleft; (3) formation of a continuous alveolar ridge to facilitate orthodontic correction of malocclusion; (4) supporting the nostril floor and alar base to improve nasal aesthetics. It has been well accepted in most craniofacial centers as routine procedure in cleft lip and palate rehabilitation. A new surgical technique for alveolar bone grafting has been introduced to the Chang Gung Craniofacial Center since July 1991. It provided a good exposure of the alveolar cleft, primary closure of the fistula and adequate volume of bone graft. A review of 27 consecutive alveolar bone grafting procedures performed in unilateral cleft lip and palate patients from July 1991 to June 1992 was presented. Patients have been followed up for at least 6 months. The alveolar bone graft was evaluated clinically and radiologically at one week, six months and one year after the surgery. The preliminary results indicated that the new surgical technique produced less chance of recurrent fistula, good postoperative gingival height, and improvement of nasal aesthetics. Based on the results of this new study we strongly advocate the use of this new surgical technique.     

Benzodiazepine use in pregnancy and major malformations or oral cleft: meta-analysis of cohort and case-control studies

OBJECTIVE: To determine if exposure to benzodiazepines during the first trimester of pregnancy increases risk of major malformations or cleft lip or palate. DESIGN: Meta-analysis. SETTING: Studies from 1966 to present. SUBJECTS: Studies were located with Medline, Embase, Reprotox, and from references of textbooks, reviews, and included articles. Included studies were original, concurrently controlled studies in any language. INTERVENTIONS: Data extraction and quality assessment were done independently and in duplicate. MAIN OUTCOME MEASURES: Maternal exposure to benzodiazepines in at least the first trimester; incidence of major malformations or oral cleft alone, measured as odds ratios and 95% confidence intervals with a random effects model. RESULTS: Of over 1400 studies reviewed, 74 were retrieved and 23 included. In the analysis of cohort studies fetal exposure to benzodiazepine was not associated with major malformations (odds ratio 0.90; 95% confidence interval 0.61 to 1. 35) or oral cleft (1.19; 0.34 to 4.15). Analysis of case-control studies showed an association between exposure to benzodiazepines and development of major malformations (3.01; 1.32 to 6.84) or oral cleft alone (1.79; 1.13 to 2.82). CONCLUSIONS: Pooled data from cohort studies showed no association between fetal exposure to benzodiazepines and the risk of major malformations or oral cleft. On the basis of pooled data from case-control studies, however, there was a significant increased risk for major malformations or oral cleft alone. Until more research is reported, level 2 ultrasonography should be used to rule out visible forms of cleft lip.