Germline variants and phenotypic spectrum in a Canadian cohort of individuals with diffuse gastric cancer.

Background: CDH1 pathogenic variants (pvs) cause most cases of inherited diffuse gastric cancer (dgc), but have low detection rates and vary geographically. In the present study, we examined hereditary causes of dgc in patients in Ontario. Methods: CDH1 testing through single-site or multi-gene panels was conducted for patients with dgc meeting the 2015 International Gastric Cancer Linkage Consortium (igclc) criteria, or with isolated dgc at less than 50 years of age, or with a strong family history of cancer identified at the Zane Cohen Centre (zcc). All CDH1-positive patients at zcc, regardless of cancer history, were summarized. Results: In 15 of 85 patients with dgc (17.6%), a pv or likely pv was identified through CDH1 single-site (n = 43) or multi-gene panel (n = 42) testing. The detection rate was 9.4% overall (8 of 85) and 11% using igclc criteria (7 of 65). No CDH1 pvs were identified in patients with isolated dgc at less than 40 years of age, but 1 pv was identified in a patient with isolated dgc at less than 50 years of age. Multi-gene panels identified 9 pvs (21.4%), including CDH1, STK11, ATM, BRCA2, MLH1, and MSH2. Review of 81 CDH1 carriers identified 10% with dgc (median age: 48 years; range: 38-59 years); 41% were unaffected (median age: 53 years; range: 26-89 years). Observed malignancies other than dgc or lobular breast cancer (lbc) included colorectal, gynecologic, kidney or bladder, prostate, testicular, and ductal breast cancers. Lobular-breast cancer was seen only in 3 families. Conclusions: In Ontario, the detection rate of CDH1 pvs in patients with dgc was low: no pvs were identified in patients with isolated dgc at less than 40 years of age, and 1 was identified in a patient with isolated dgc at less than 50 years of age. Isolated lbc with no dgc was observed in CDH1-positive families, as were pathology-confirmed nondgc or non-lbc malignancies, which had not previously been reported. Given a phenotype that overlaps with other hereditary conditions, multi-gene panels are recommended for all patients with dgc at less than 50 years of age and for those meeting igclc criteria.

Autism severity is associated with child and maternal MAOA genotypes.

Autism severity is associated with child and maternal MAOA genotypes. We replicated and extended a previously reported association between autism severity and a functional polymorphism in the monoamine oxidase A (MAOA) promoter region, MAOA-uVNTR, in a sample of 119 males, aged 2-13 years, with autism spectrum disorder from simplex families. We demonstrated that (i) boys with the low activity 3-repeat MAOA allele had more severe sensory behaviors, arousal regulation problems, and aggression, and worse social communication skills than males with the high activity allele; and (ii) problems with aggression, as well as with fears and rituals, were modified by the mothers' genotype. Boys with the 4-repeat high activity allele who had homozygous 4-repeat mothers showed increased severity of these behaviors relative to those born to heterozygous mothers. These findings indicate the importance of considering maternal genotype in examining associations of MAOA and other genes with behavior in male offspring.

Face-brain asymmetry in autism spectrum disorders.

The heterogeneity of autism spectrum disorders (ASDs) confounds attempts to identify causes and pathogenesis. Identifiable endophenotypes and reliable biomarkers within ASDs would help to focus molecular research and uncover genetic causes and developmental mechanisms. We used dense surface-modelling techniques to compare the facial morphology of 72 boys with ASD and 128 first-degree relatives to that of 254 unrelated controls. Pattern-matching algorithms were able to discriminate between the faces of ASD boys and those of matched controls (AUC=0.82) and also discriminate between the faces of unaffected mothers of ASD children and matched female controls (AUC=0.76). We detected significant facial asymmetry in boys with ASD (P<0.01), notably depth-wise in the supra- and periorbital regions anterior to the frontal pole of the right hemisphere of the brain. Unaffected mothers of children with ASD display similar significant facial asymmetry, more exaggerated than that in matched controls (P<0.03) and, in particular, show vertical asymmetry of the periorbital region. Unaffected fathers of children with ASD did not show facial asymmetry to a significant degree compared to controls. Two thirds of unaffected male siblings tested were classified unseen as more facially similar to unrelated boys with ASD than to unrelated controls. These unaffected male siblings and two small groups of girls with ASD and female siblings, all show overall directional asymmetry, but without achieving statistical significance in two-tailed t-tests of individual asymmetry of ASD family and matched control groups. We conclude that previously identified right dominant asymmetry of the frontal poles of boys with ASD could explain their facial asymmetry through the direct effect of brain growth. The atypical facial asymmetry of unaffected mothers of children with ASD requires further brain studies before the same explanation can be proposed. An alternative explanation, not mutually exclusive, is a simultaneous and parallel action on face and brain growth by genetic factors. Both possibilities suggest the need for coordinated face and brain studies on ASD probands and their first-degree relatives, especially on unaffected mothers, given that their unusual facial asymmetry suggests an ASD susceptibility arising from maternal genes.

Cryptic duplication of 21q in an individual with a clinical diagnosis of Down syndrome.

We describe an adult male who was diagnosed with Down syndrome (DS) at 9 months of age, but had repeatedly normal karyotypes until recent mid-resolution chromosome studies showed a possible duplication of 21q22.13 to 21q22.3. The abnormality was investigated using fluorescent in situ hybridization (FISH) studies. These showed hybridization of a whole chromosome paint probe (wcp21, Oncor Coatasome 21) to the entire length of both chromosome 21 homologues and one very large hybridization signal of a cosmid contig probe localized within bands 21q22.13-21q22.2(LSI-21, Vysis) on the ?dup(21q) homologue. CGH analysis identified a ratio of 1.5 for the segment of chromosome 21 involving band 21q22, indicating a gain of part, or all, of the terminal band of chromosome 21. The karyotype was thus defined as 46,XY,?dup(21) (q22.13q22.2).ish dup(21)(LSI-21++,wcp21+). Common DS characteristics in our case and 12 previously reported cases with duplications involving chromosome 21 included mental retardation, fifth finger clinodactyly, open mouth and oblique eye fissures. Transverse palmar creases and congenital heart defects, seen in DS less than 40% of the time, were infrequent. Presence of these features did not appear to depend on the specific portion of chromosome 21 that was duplicated. A review of 18 additional clinical features showed no consistent phenotype-genotype correlations.

The aromatic hydrocarbon receptor for 2,3,7,8-tetrachlorodibenzo-p-dioxin and variable levels of induced aryl hydrocarbon hydroxylase activity in clones of mouse hepatoma cells.

Induction of aryl hydrocarbon hydroxylase (AHH) activity was studied in clones and subclones of mouse hepatoma (Hepa-lcl) cells. When maximally induced, one clone had significantly lower (p less than 0.005), two had approximately the same, and two had significantly higher (p less than 0.005) levels of AHH activity compared with Hepa-lcl. The maximal level of induced activity, relative to the parent population, in two clones chosen for further analysis was 0.14 +/- 0.09 for clone 1 (Hs-1) and 0.94 +/- 0.28 for clone 9 (Hs-9). These relative levels were stable over a period of 10 months and were similar when activity was induced either with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or benz[a]anthracene. Subclones of Hepa-lcl cells, derived from the Hs-9 clone, also demonstrated variation in induced AHH activity. When maximally induced with TCDD, six subclones had significantly lower AHH activity (p less than 0.005), two had approximately the same, and one had significantly higher levels (p less than 0.005) compared with the progenitor Hs-9 population. Comparative analysis of Ah receptor characteristics in two unselected clones of Hepa-lcl with significantly different levels of AHH activity demonstrated that there was no apparent correlation between relative level of induced AHH activity and (i) total quantity of Ah receptor (cytosol and nuclear), (ii) receptor affinity for TCDD and number of receptor sites in each cell, (iii) subcellular distribution of [3H]TCDD, or (iv) specificity and saturable nature of binding. Coordinate measurement of the concentration of nuclear receptor and absolute induced AHH activity in Hepa-lcl and its clones had a positive correlation (r = 0.79).

A linkage study of primary affective disorder.

Marker loci in 113 members of nine unrelated multiplex families identified by a bipolar proband were tested for linkages with primary affective disorder. Linkage was excluded between the disease locus (assuming that it was a single autosomal dominant gene) and the HLA loci at a recombination fraction of 0.2, the ABO, Rh, and Lu loci at almost 0.05 and the Fy and P loci at 0.001.

Linkage studies of Friedreich ataxia by means of blood-group and protein markers.

Friedreich ataxia (FA) is an autosomal recessive, neuro-degenerative disorder in which the pathogenetic mechanism remains unidentified despite extensive biochemical studies. Genetic-linkage studies provide an alternative approach to determining the basic defect. Linkage analysis between FA and 36 polymorphic-blood-group and protein markers has been carried out on three separate patient populations--16 families from the inbred Acadian population of Louisiana, 21 French-Canadian families from Quebec, and nine apparently unrelated British families--in an attempt to determine the chromosomal location of the disease mutation. Neither evidence of linkage to any of the markers investigated nor heterogeneity among the populations was found for any of the comparisons. The negative lod scores exclude the locus for FA from greater than 20% of the genome.

An assessment of the use of flanking DNA markers for fra(X) syndrome carrier detection and prenatal diagnosis.

One hundred and three individuals in 11 unrelated families with the fragile-X [fra(X)] syndrome were tested for polymorphisms identified by probes flanking the fra(X) site at Xq27.3. Two probes distal and 2 proximal to the fra(X) site were used. Thirteen known female carriers were analyzed retrospectively. DNA markers gave probabilities of carrying the mutation of 99% in 1 female, 89% in 8 females, and 10-55% in the other 4 females. We also estimated the probability of having inherited the mutation for 16 individuals of unknown fra(X) status using DNA markers and corrections for incomplete penetrance. The DNA marker test gave risks for females of 1-6% (7 females), 15% (1 female), and 97% (1 female). In males the risks were 1-3% (6 males) and 91% (1 male). In 3 families, DNA marker data were used to calculate probabilities of greater than or equal to 98.5% that transmission of the fra(X) mutation had occurred through normal males. In the retrospective studies, only 1 of 7 retarded males could have been diagnosed prenatally as having the fra(X) mutation with a probability of 99%. DNA marker analysis was uninformative in 5 of these males. When fra(X) carrier status cannot be established by chromosome analysis, DNA marker studies provide an alternative test that can be used to calculate individual risks more precisely. However, linkage analysis of the probe loci in these 11 families suggests that the recombination frequency between the fra(X) locus and the factor IX gene (F9) and DXS52 may be greater than previously suggested. Until the true recombination frequencies are established and the question of heterogeneity among families is fully analyzed, caution in using DNA markers as a predictive test is advised.

The genetic distance between the coagulation factor IX gene and the locus for the fragile X syndrome: clinical implications.

In 3 families with the fragile-X [fra(X)] syndrome, we have identified a minimum of 4 recombinations in 9 meioses between the syndrome locus and the coagulation Factor IX gene. Two Factor IX intragenic restriction fragment length polymorphisms (RFLPs), produced with TaqI and XmnI, were used as markers. In lod score calculations, incomplete penetrance of the fra(X) mutation in males and females was taken into account by the computer program LIPED. The cumulative maximum lod score calculated from these data and from data previously reported was 2.75 at a recombination frequency of 20% (theta = 0.20). This indicates that the genetic distance between the Factor IX gene and the fra(X) locus is too great for Factor IX probes to be used alone for carrier detection in the fra(X) syndrome. Additional polymorphic loci more tightly linked to the fra(X) syndrome locus are required.

Genetic mapping of DNA segments relative to the locus for the fragile-X syndrome at Xq27.3.

We have tested linkage between the locus for the fragile-X [fra(X)] syndrome at Xq27.3 and five polymorphic restriction sites identified by four DNA probes mapping distal to Xq26.1. A maximum distance of approximately 15 centimorgans (cM) between Xq27.3 and the marker loci mapping to this region was predicted based on the physical chromosome length. Close linkage between the disease and marker loci was excluded for probes DXS19 and DXS37 (theta = .05, Z = -2.94 and Z = -4.17, respectively). These marker loci were estimated to be less than five cM apart but approximately 40 cM proximal to the fragile site, indicating that there is a significantly greater frequency of recombination in this region of the X chromosome than expected from the physical length. Linkage results for the other marker loci and the fra(X) syndrome were inconclusive. However, the pX45d probe locus appears very closely linked to the factor IX locus (Z = 1.94 at theta = 0) and is approximately 20 cM proximal to Xq27.3. A relative map of the polymorphic restriction sites, fra(X) syndrome locus, and factor IX locus was constructed by maximizing lod scores over the Xq26.1----q27.3 region.