Sluggish cognitive tempo in children and adolescents with higher functioning autism spectrum disorders: Social impairments and internalizing symptoms

Sluggish cognitive tempo (SCT) was introduced in 1980s in the field of attention deficit hyperactivity disorder (ADHD). Studies indicate that symptoms of SCT are separate from symptoms of ADHD and independently associated with multiple domains of functioning in clinical groups and in typical development. We assessed whether similar pattern would apply to higher functioning autism spectrum disorders (ASD). Children with higher functioning ASD (N = 55; 5-15 years) were divided into the ASD+High SCT (n = 17), the ASD+Medium SCT (n = 18) and the ASD+Low SCT (n = 20) groups based on parent-rated daydreaming and slowness on the Five to Fifteen questionnaire (FTF). The groups were compared on SCT-related impairments found in previous studies: social skills, academic functioning, psychiatric symptoms, and processing speed. Assessment methods were the FTF, the Development and Well-Being Assessment, and the Coding subtest of the WISC-III. The ADHD symptoms were statistically controlled due to the overlap between SCT and ADHD. The ASD+High SCT and ASD+Medium SCT groups were significantly more likely to have the most pronounced social impairments, and the ASD+High SCT group had significantly higher rate of internalizing disorders compared to the ASD+Low SCT group. Our results suggest that children with higher functioning ASD and high or medium levels of SCT symptoms could be at higher risk for psychosocial impairments than children with higher functioning ASD with low levels of SCT symptoms. Co-occurring ADHD symptoms do not explain the finding. Recognizing SCT symptoms in higher functioning ASD would be important to targeting preventive support.

Adenomatous polyposis families that screen APC mutation-negative by conventional methods are genetically heterogeneous

PURPOSE

One third of families with classical adenomatous polyposis (FAP), and a majority of those with attenuated FAP (AFAP), remain APC mutation-negative by conventional methods. Our purpose was to clarify the genetic basis of polyposis and genotype-phenotype correlations in such families.

PATIENTS AND METHODS

We studied a cohort of 29 adenomatous polyposis families that had screened APC mutation-negative by the protein truncation test, heteroduplex analysis, and exon-specific sequencing. The APC gene was investigated for large genomic rearrangements by multiplex ligation-dependent probe amplification (MLPA), and for allelic mRNA expression by single nucleotide primer extension (SNuPE). The AXIN2 gene was screened for mutations by sequencing.

RESULTS

Four families (14%) showed a constitutional deletion of the entire APC gene (three families) or a single exon (one family). Seven families (24%) revealed reduced or extinct mRNA expression from one APC allele in blood, accompanied by loss of heterozygosity in the APC region in six (75%) of eight tumors. In 15 families (52%), possible APC involvement could be neither confirmed nor excluded. Finally, as detailed elsewhere, three families (10%) had germline mutations in genes other than APC, AXIN2 in one family, and MYH in two families.

CONCLUSION

"APC mutation-negative" FAP is genetically heterogeneous, and a combination of MLPA and SNuPE is able to link a considerable proportion (38%) to APC. Significant differences were observed in clinical manifestations between subgroups, emphasizing the importance of accurate genetic and clinical characterization for the proper management of such families.

Molecular analysis of familial endometrial carcinoma: a manifestation of hereditary nonpolyposis colorectal cancer or a separate syndrome?

PURPOSE

Familial clustering of endometrial carcinoma (EC) may occur as part of hereditary nonpolyposis colorectal cancer (HNPCC), a multiorgan cancer syndrome with mismatch repair (MMR) deficiency. Clustering of EC alone, termed as familial site-specific EC, may constitute a separate entity. Because its genetic basis is unknown, our purpose was to characterize such families molecularly.

MATERIALS AND METHODS

Twenty-three families with site-specific EC were identified among 519 consecutive patients diagnosed with EC during 1986 to 1997. Tumor tissues were examined for MMR protein expression by immunohistochemical (IHC) analysis, and MMR genes pinpointed by IHC changes were screened for germline mutations by exon-by-exon sequencing, multiplex ligation-dependent probe amplification, and direct tests for mutations common in the population.

RESULTS

Among 33 ECs from 23 families, MLH1 protein was lost in seven tumors (21%), MSH2 together with MSH6 was lost in four tumors (12%), and MSH6 alone was lost in five tumors (15%). A truncating germline mutation in MSH6 (3261insC) was identified in one family and a likely pathogenic missense mutation in MSH2 (D603N) was identified in another family. Among the original 519 patients, nine (all with colon cancer in the family) were diagnosed with HNPCC at the outset-six with MLH1 and three with MSH2 mutations.

CONCLUSION

Our study gives a minimum overall frequency of 2.1% (11 of 519) for germline MMR defects ascertained through EC in the index patients. The fact that only two of 23 families with site-specific EC (8.7%) had germline mutations in MMR genes suggests another as yet unknown etiology in most families with site-specific EC.

Endometrial and colorectal tumors from patients with hereditary nonpolyposis colon cancer display different patterns of microsatellite instability

The colorectum and uterine endometrium are the two most commonly affected organs in hereditary nonpolyposis colon cancer (HNPCC), but the genetic basis of organ selection is poorly understood. As tumorigenesis in HNPCC is driven by deficient DNA mismatch repair (MMR), we compared its typical consequence, instability at microsatellite sequences, in colorectal and endometrial cancers from patients with identical predisposing mutations in the MMR genes MLH1 or MSH2. Analysis of non-coding (BAT25, BAT26, and BAT40) and coding mononucleotide repeats (MSH6, MSH3, MLH3, BAX, IGF2R, TGF beta RII, and PTEN), as well as MLH1- and MSH2-linked dinucleotide repeats (D3S1611 and CA7) revealed significant differences, both quantitative and qualitative, between the two tumor types. Whereas colorectal cancers displayed a predominant pattern consisting of instability at the BAT loci (in 89% of tumors), TGF beta RII (73%), dinucleotide repeats (70%), MSH3 (43%), and BAX (30%), no such single pattern was discernible in endometrial cancers. Instead, the pattern was more heterogeneous and involved a lower proportion of unstable markers per tumor (mean 0.27 for endometrial cancers versus 0.45 for colorectal cancers, P < 0.001) and shorter allelic shifts for BAT markers (average 5.1 bp for unstable endometrial cancers versus 9.3 bp for colorectal cancers, P < 0.001). Among the individual putative "target" loci, PTEN instability was associated with endometrial cancers and TGF beta RII instability with colon cancers. The different instability profiles in endometrial and colorectal cancers despite identical genetic predisposition underlines organ-specific differences that may be important determinants of the HNPCC tumor spectrum.

Lack of MSH2 and MSH6 characterizes endometrial but not colon carcinomas in hereditary nonpolyposis colorectal cancer

Hereditary nonpolyposis colorectal cancer syndrome is associated with an inherited predisposition to primarily colorectal cancer (CRC) and endometrial cancer (EC); however, the biological basis of the organ involvement remains unknown. As an attempt to explore whether the expression levels of MLH1, MSH2, and MSH6 may play a role, we used immunohistochemistry to study 42 ECs and 35 CRCs from patients carrying the same predisposing mutations. Among MSH2 mutation carriers, MLH1 was expressed in both tumor types, whereas MSH2 and, in many cases, also MSH6, were absent. Remarkably, among MLH1 mutation carriers, 54% of ECs (21 of 39), but none of the CRCs (0 of 32), lacked the MSH2 and/or MSH6 protein in addition to lacking MLH1 protein expression. These results demonstrate a marked difference between hereditary nonpolyposis colorectal cancer-related CRCs and ECs and suggest that the development of the latter tumors is selectively associated with the MSH2/MSH6 protein complex deficiency.

Microsatellite instability in adenomas as a marker for hereditary nonpolyposis colorectal cancer

Hereditary nonpolyposis colorectal cancer (HNPCC) is the most common of the well-defined colorectal cancer syndromes, accounting for at least 2% of the total colorectal cancer burden and carrying a greater than 80% lifetime risk of cancer. Significant reduction in cancer morbidity and mortality can be accomplished by appropriate clinical cancer screening of HNPCC patients with mutations in mismatch repair (MMR) genes. Thus, it is desirable to identify individuals who are mutation-positive. In individuals with cancer, mutation detection can be accomplished relatively efficiently by germline mutation analysis of individuals whose cancers show microsatellite instability (MSI). This study was designed to assess the feasibility of screening colorectal adenoma patients for HNPCC in the same manner. Among 378 adenoma patients, six (1.6%) had at least one MSI adenoma. Five out of the six patients (83%) had a germline MMR gene mutation. We conclude that MSI analysis is a useful method of prescreening colorectal adenoma patients for HNPCC.

Genetic polymorphisms in carcinogen metabolism and their association to hereditary nonpolyposis colon cancer

BACKGROUND & AIMS

The phenotype of hereditary nonpolyposis colorectal cancer shows interfamilial and intrafamilial variation even in the presence of identical predisposing mutations, suggesting the existence of additional phenotype determinants. The modifying role of genetic polymorphisms in loci involved in carcinogen metabolism was studied.

METHODS

We focused on colon cancers from kindreds sharing one of two predisposing mutations (mutation 1 or 2) in the mismatch repair gene MLH1 (78 and 14 tumors, respectively). Polymorphisms in N-acetyltransferase 1 (NAT1) and glutathione S-transferase (GST) M1 and GSTT1 were investigated.

RESULTS

The NAT1 allele 10 was associated with lower median age at diagnosis in both groups. In mutation 1 group, the NAT1 allele 10 was a risk factor for distal tumor location, both alone (P = 0.028) and combined with the GSTT1-positive genotype (P = 0.008). On the other hand, the combined null genotype of GSTM1 and GSTT1 was associated with proximal tumors. Associations with tumor location were not observed in patients with mutation 2, probably reflecting a small sample size.

CONCLUSIONS

The results suggest that genetic polymorphisms in carcinogen metabolism modify the age of onset and tumor location in individuals with inherited deficiency of DNA mismatch repair.

Age and origin of two common MLH1 mutations predisposing to hereditary colon cancer

Two mutations in the DNA mismatch repair gene MLH1, referred to as mutations 1 and 2, are frequent among Finnish kindreds with hereditary nonpolyposis colorectal cancer (HNPCC). In order to assess the ages and origins of these mutations, we constructed a map of 15 microsatellite markers around MLH1 and used this information in haplotype analyses of 19 kindreds with mutation 1 and 6 kindreds with mutation 2. All kindreds with mutation 1 showed a single allele for the intragenic marker D3S1611 that was not observed on any unaffected chromosome. They also shared portions of a haplotype of 4-15 markers encompassing 2.0-19.0 cM around MLH1. All kindreds with mutation 2 shared another allele for D3S1611 and a conserved haplotype of 5-14 markers spanning 2.0-15.0 cM around MLH1. The degree of haplotype conservation was used to estimate the ages of these two mutations. While some recessive disease genes have been estimated to have existed and spread for as long as thousands of generations worldwide and hundreds of generations in the Finnish population, our analyses suggest that the spread of mutation 1 started 16-43 generations (400-1,075 years) ago and that of mutation 2 some 5-21 generations (125-525 years) ago. These datings are compatible with our genealogical results identifying a common ancestor born in the 16th and 18th century, respectively. Overall, our results indicate that all Finnish kindreds studied to date showing either mutation 1 or mutation 2 are due to single ancestral founding mutations relatively recent in origin in the population. Alternatively, the mutations arose elsewhere earlier and were introduced in Finland more recently.

DNA mismatch repair gene mutations in 55 kindreds with verified or putative hereditary non-polyposis colorectal cancer

The DNA mismatch repair genes MSH2 and MLH1 have been shown to account for a major share of hereditary non-polyposis colorectal cancer (HNPCC). We searched for germline mutations in these genes in 35 HNPCC kindreds fulfilling the Amsterdam diagnostic criteria and in a further 20 kindreds with an average of four affected members per family but not meeting the formal criteria. We first screened for truncations by reverse transcriptase (RT)-PCR. If no mutation was found, we screened genomic DNA by a novel application of two-dimensional (2-D) DNA electrophoresis that allows the simultaneous study of all exons of each gene. All abnormalities were followed up by sequencing. Eight different pathogenic germline mutations were found, two in MSH2 and six in MLH1. We report three major conclusions. First, these mutations together accounted for 86% (30/35) of the kindreds meeting the Amsterdam criteria, but only 30% (6/20) of the remaining kindreds, suggesting differences in etiology. Second, MLH1 was involved in > 90% (34/36) of kindreds with a known predisposing mutation, suggesting that mutations in the MLH1 gene are responsible for most HNPCC kindreds in Finland. Third, our results indicate that the successive application of RT-PCR and 2-D DNA electrophoresis is a sensitive and efficient method for mutation screening in typical HNPCC.

Founding mutations and Alu-mediated recombination in hereditary colon cancer

By screening members of Finnish families displaying hereditary nonpolyposis colorectal cancer (HNPCC) for predisposing germline mutations in MSH2 and MLH1, we show that two mutations in MLH1 together account for 63% (19/30) of kindreds meeting international diagnostic criteria. Mutation 1, originally detected as a 165-base pair deletion in MLH1 cDNA comprising exon 16, was shown to consist of a 3.5-kilobase genomic deletion most likely resulting from Alu-mediated recombination. Mutation 2 destroys the splice acceptor site of exon 6. A simple diagnostic test based on polymerase chain reaction was designed for both mutations. Our results show that these two ancestral founding mutations account for a majority of Finnish HNPCC kindreds and represent the first report of Alu-mediated recombination causing a prevalent, dominantly inherited predisposition to cancer.