Abstract P1-08-02: CYP2D6 gene variants and effectiveness of adjuvant tamoxifen in breast cancer: A population-based case-control study

Tamoxifen, a cornerstone of adjuvant therapy for hormone-receptor-positive breast cancer, is metabolized to the active metabolite endoxifen through enzymatic activity of cytochrome P450 2D6. CYP2D6 has numerous alleles that affect metabolizing phenotype. Among women who take tamoxifen, those homozygous for inactive alleles (poor metabolizers) have lower levels of serum endoxifen than those with two functional alleles (extensive metabolizers). Several studies have reported increased risk of breast cancer recurrence or death in women homozygous for CYP2D6 inactive alleles, but others have found no association between CYP2D6 function and outcome. We explored this question in the large member population of the Kaiser Permanente Northwest (KPNW) integrated health plan. We conducted a population-based case-control study to evaluate the hypothesis that, after adjuvant tamoxifen treatment for breast cancer, women with CYP2D6 genotypes associated with poor metabolism of tamoxifen have an elevated risk of breast cancer recurrence compared to women with CYP2D6 genotypes associated with extensive metabolism of tamoxifen. We further hypothesized that women with CYP2D6 genotypes associated with intermediate metabolism of tamoxifen are at intermediate risk of recurrence. Study subjects were women who were diagnosed from 1980 to 2011 with hormone-receptor positive breast cancer, who received at least 180 days of adjuvant tamoxifen treatment, and for whom stored formalin-fixed paraffin-embedded (FFPE) normal tissue was available for laboratory analysis. Cases (358) were women with breast cancer recurrence recorded in the KPNW Tumor Registry and validated by medical record review. Randomly selected controls (833), without recurrent breast cancer, were matched to cases on tumor stage, diagnosis year, diagnosis age, race/ethnicity, and patterns of health plan membership. We collected data from medical records and from pharmacy, laboratory, tumor registry, and membership health plan databases. The Oregon Health & Science University Molecular Genetics Laboratory extracted genomic DNA from stored FFPE tissue blocks and performed allelic discrimination assays and pyrosequencing to accurately determine CYP2D6 variant status for the alleles, *3, *4, *5, *10, *17, and *41. All assays have been completed and study subjects have been categorized according to CYP2D6 metabolizer phenotype (poor, intermediate, extensive) and activity score (0-2). Based on the ethnicities in our study population, the CYP2D6 allele frequencies are in Hardy-Weinberg equilibrium, and the frequencies of the predicted metabolizer phenotypes also fall within the expected range. Using multivariable logistic regression analysis, we will assess CYP2D6 functional status and activity score in relation to breast cancer recurrence, taking into account factors that may alter the association, including tamoxifen dose and duration of use, as well as concomitant medications that alter the activity of the CYP2D6 enzyme. Results will be available by 12/1/2015.

Citation Format: Weinmann S, Richert–Boe K, Goddard K, Chen C, Punj S, Schwarzkopf D, Kalter M, Richards CS. CYP2D6 gene variants and effectiveness of adjuvant tamoxifen in breast cancer: A population-based case-control study. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-08-02.

The major genetic determinants of HIV-1 control affect HLA class I peptide presentation

Infectious and inflammatory diseases have repeatedly shown strong genetic associations within the major histocompatibility complex (MHC); however, the basis for these associations remains elusive. To define host genetic effects on the outcome of a chronic viral infection, we performed genome-wide association analysis in a multiethnic cohort of HIV-1 controllers and progressors, and we analyzed the effects of individual amino acids within the classical human leukocyte antigen (HLA) proteins. We identified >300 genome-wide significant single-nucleotide polymorphisms (SNPs) within the MHC and none elsewhere. Specific amino acids in the HLA-B peptide binding groove, as well as an independent HLA-C effect, explain the SNP associations and reconcile both protective and risk HLA alleles. These results implicate the nature of the HLA-viral peptide interaction as the major factor modulating durable control of HIV infection.

Data quality in thermal summation development models for forensically important blowflies

To highlight some issues regarding data quality that are significant in estimating post-mortem intervals (PMI) from maggots, the developmental constants of thermal summation models for development of Chrysomya megacephala Fabricius (Diptera: Calliphoridae) were calculated from incidental data gathered from 12 published studies, and from data generated specifically for the purpose in a single experiment. The focused experiment involved measuring the timing of five developmental landmarks at nine constant temperatures with a sampling resolution of 6-12 h, which is characteristic of other published studies. Combining data from different studies produced inconsistent results because of statistical noise introduced by (at least) disparities in temporal precision, descriptive statistics, geographical location and rearing diets. A robust experimental design to estimate a developmental model should involve at least six constant temperatures, starting at about 7 degrees C above the relevant developmental zero (D0) and going almost to the upper critical temperature, and a temporal sampling interval with a relative precision of about 10%, which requires sampling about every 2 h until hatching, about every 3 h until first ecdysis and about every 6 h until second ecdysis.

Models of development for blowfly sister species Chrysomya chloropyga and Chrysomya putoria

Developmental curves for the sister species Chrysomya chloropyga (Wiedemann, 1818) and Chrysomya putoria (Wiedemann, 1830) (Diptera: Calliphoridae) were established at eight and 10 different constant temperatures, respectively, using developmental landmarks and body length as measures of age. The thermal summation constants (K) and developmental threshold (D(0)) were calculated for five developmental landmarks using a previously described method. Isomorphen and isomegalen diagrams were also constructed for the purpose of estimating postmortem intervals (PMIs). Chrysomya chloropyga had an average developmental threshold value (D(0)) of 10.91 degrees C (standard error [SE] = 0.94 degrees C, n = 5), significantly lower than that of C. putoria (13.42 degrees C, SE = 0.45 degrees C, n = 5) (paired t-test: t = - 4.63, d.f. = 8, P < 0.00). Similarly, K values for C. chloropyga were larger than those for C. putoria for all developmental events except onset of the wandering phase. These are the first data that can be used to calculate minimum PMIs and predict population growth of C. chloropyga and C. putoria in Africa; the data indicate that developmental data for one of these species cannot be used as surrogate data for the sister species.

Genetics of Biomphalaria glabrata and its effect on the outcome of Schistosoma mansoni infection

The genetics of the snail Biomphalaria glabrata is better characterized than that of any other intermediate host of schistosomes of humans. Using techniques of selective breeding, several snail stocks have been developed that consistently display resistant or susceptible phenotypes. Investigators using these stocks have learned that several snail and parasite genes influence the course of parasite development. Here, Charles Richards, Matty Knight and Fred Lewis discuss the importance of the snail's genetics in categorizing resistance in this complex invertebrate, some recent molecular evidence that may help us understand several of the problems that still remain, and some challenges lying ahead for investigators in this field.

Oviposition by small hive beetles elicits hygienic responses from Cape honeybees

Two novel behaviours, both adaptations of small hive beetles ( Aethina tumida Murray) and Cape honeybees ( Apis mellifera capensis Esch.), are described. Beetles puncture the sides of empty cells and oviposit under the pupae in adjoining cells. However, bees detect this ruse and remove infested brood (hygienic behaviour), even under such well-disguised conditions. Indeed, bees removed 91% of treatment brood (brood cells with punctured walls caused by beetles) but only 2% of control brood (brood not exposed to beetles). Only 91% of treatment brood actually contained beetle eggs; the data therefore suggest that bees remove only that brood containing beetle eggs and leave uninfected brood alone, even if beetles have accessed (but not oviposited on) the brood. Although this unique oviposition strategy by beetles appears both elusive and adaptive, Cape honeybees are able to detect and remove virtually all of the infested brood.

Diagnostic DNA testing for X-linked ocular albinism (OA1) with a hierarchical mutation screening protocol

Albinism is a group of inherited conditions in which affected individuals have less than normal pigment in the eyes, skin, and hair compared to others of the same race and ethnic background. The prevalence of all types of albinism in the United States is estimated at 1 in 20,000, based on poor epidemiological data. X-linked Nettleship-Falls ocular albinism (XLOA, OA1) affects approximately 1/150,000 males in the population. XLOA effects reduce visual acuity and nystagmus, result in a mild skin and hair phenotype, and occur mostly in XY males. Female carriers of XLOA have normal visual acuity, but often show iris punctate transillumination and a classic pattern of mosaic retinal pigmentation, coarse and grainy in the macula and becoming increasingly reticular into the periphery of the retinal pigment epithelium. Studies of OA1 have shown linkage of a single gene to markers at Xp22.3-p22.2. About 48% of the reported mutations in the OA1 gene are intragenic deletions and about 43% are point mutations. We present a hierarchical strategy for mutation screening for diagnostic testing for OA1 that comprises two tiers: first, multiplex PCR to detect intragenic deletions in the OA1 gene with denaturing high-performance liquid chromatography (dHPLC), and, second, heteroduplex analysis with dHPLC to scan for mutations, with subsequent sequencing of variants to confirm putative mutations in the OA1 gene. Prenatal diagnosis can be provided for families when the mutation has been firmly identified. We have validated this procedure with positive controls that were identified in patients by Southern blot, single-stranded conformation polymorphism (SSCP), and sequencing. In this hierarchical strategy, these procedures have an analytical sensitivity of > 99%.

Detection of sequence variations in the adenomatous polyposis coli (APC) gene using denaturing high-performance liquid chromatography

We have evaluated the usefulness of denaturing high performance liquid chromatography (dHPLC) for scanning the adenomatous polyposis coli (APC) gene for point mutations, small deletions, and insertions. Our assay consists of 28 sets of primers to amplify the 15 exons of the APC gene. All PCR reactions were amplified simultaneously using the same reaction conditions in a 96-well format and then analyzed by dHPLC, using empirically determined optimum temperatures for partial fragment denaturation. Previously studied DNA specimens from 47 familial adenomatous polyposis (FAP) patients were analyzed by dHPLC and all mutations were correctly identified and confirmed by sequence analysis. This approach identified a single-base substitution in exon 6 and a 2-bp insertion in exon 15 that initially had not been detected by single-strand conformational polymorphism (SSCP) analysis. A novel mutation in exon 15 of the APC gene, 2065delG (codon 689) that had previously been undetected by the protein truncation test (PTT) was also identified by dHPLC. We present our validation studies of dHPLC technology for APC gene analysis in terms of sensitivity and specificity and compare it to current standard scanning technologies including PTT, SSCP, and conformational sensitive gel electrophoresis (CSGE).

The relationship between Schistosoma mansoni and Biomphalaria glabrata: genetic and molecular approaches

Biomphalaria glabrata is a major intermediate host for the helminth parasite Schistosoma mansoni. Beginning in the mid-20th century, studies were carried out with this snail species to identify the immunological and genetic components that might be involved in controlling schistosome development. A number of genetically well-defined snail stocks were derived as a direct result of these studies and have since played major roles in helping investigators to identify important cellular and humoral components in the snail/schistosome relationship. This review will explore the historical development of these stocks and describe some of the major advances in several areas of medical malacology that hawe been made possible be their use.

Technical standards and guidelines for fragile X: the first of a series of disease-specific supplements to the Standards and Guidelines for Clinical Genetics Laboratories of the American College of Medical Genetics. Quality Assurance Subcommittee of the Laboratory Practice Committee

Preface:

The Quality Assurance subcommittee of the ACMG Laboratory Practice committee has the mission of maintaining high technical standards for the performance and interpretation of genetic tests. In part, this is accomplished by the publication of the document “Standards and Guidelines for Clinical Genetics Laboratories,” which was published in its second edition in 1999 and is now maintained online (see www.faseb.org/genetics/acmg/index.html ). This subcommittee also reviews the outcome of national proficiency testing in the genetics area and may choose to focus on specific diseases or methodologies in response to those results. Accordingly, the subcommittee selected fragile X syndrome to be the first topic in a new series of supplemental sections, recognizing that it is one of the most frequently ordered genetic tests and that it has many alternative methods with different strengths and weaknesses. This document follows the outline format of the general Standards and Guidelines. It is designed to be a checklist for genetic testing professionals who are already familiar with the disease and the methods of analysis.

Abnormal uterine bleeding. Diagnostic considerations, management options

The approach to diagnosis of abnormal uterine bleeding is guided by a sound knowledge of menstrual physiology and differential diagnosis. Often, simple anovulation is the underlying problem, although the possibility of pregnancy, endometrial hyperplasia with atypia, or benign reproductive tract disease must be considered. In the majority of cases, abnormal uterine bleeding can be fully evaluated and effectively treated medically without the need for gynecologic referral.

Mammography behavior after receiving a negative BRCA1 mutation test result in the Ashkenazim: a community-based study

PURPOSE

To define the impact of a negative BRCA1 test result on subsequent breast cancer screening behavior in women.

METHODS

Longitudinal study of a community-based sample of Ashkenazi Jews offered testing for the 185delAG BRCA1 mutation in 1996. Of 309 participants, 118 women were mutation negative, of average risk (based on family history of cancer), unaffected with breast cancer, and provided complete data at baseline, and Year 1 and Year 2 follow-up questionnaires.

RESULTS

Women age 50 and older had 91.7% compliance with mammography for the year prior to entry (baseline), 88.3% during Year 1, 91.7% during Year 2 (no significant change; P = 0.775). Women under age 50 demonstrated an increase in mammography (49.2% at baseline, 62.7% Year 1, and 67.1% Year 2; P = 0.035). Both groups demonstrated significant decreases in breast cancer worry and perceived risk. Logistic regression analysis on having a mammogram at Year 2 showed that age, physician recommendation, worry, and perceived risk were all significant.

CONCLUSION

Receipt of negative BRCA1 test results in a cohort of Ashkenazi Jewish women did not have a negative impact on mammography behavior 2 years after genetic testing.

Identification of female carriers for Duchenne and Becker muscular dystrophies using a FISH-based approach

Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are X-linked recessive neuromuscular diseases caused by dystrophin gene mutations. Deletions, or more rarely duplications, of single or multiple exons within the dystrophin gene can be detected by current molecular methods in approximately 65% of DMD patients. Mothers of affected males have a two-thirds chance of carrying a dystrophin mutation, whilst approximately one-third of affected males have de novo mutations. Currently, Southern blot analysis and multiplex PCR directed against exons in deletion hot spots are used to determine female carrier status. However, both of these assays depend on dosage assessment to accurately identify carriers since, in females, the normal X chromosome is also present. To obviate quantitation of gene dosage, we have developed exon-specific probes from the dystrophin gene and applied them to a screen for potential carrier females using fluorescence in situ hybridization (FISH). Cosmid clones, representing 16 exons, were identified and used in FISH analysis of DMD/BMD families. Our preliminary work has identified multiple, informative probes for several families with dystrophin deletions and has shown that a FISH-based assay can be an effective and direct method for establishing the DMD/BMD carrier status of females.

Estimated contribution of known ataxia genes in ataxia patients undergoing DNA testing

We estimated the relative contributions of known ataxia genes (SCA1, 2, 3, 6, 7 and X25) in the patient population sent to our DNA diagnostic laboratory for diagnostic testing. Approximately 28% of these patients had an abnormal triplet repeat expansion in one of these ataxia genes (3% for SCA1, 8% for SCA2, 11% for SCA3/MJD, 2% for SCA6, 3% for SCA7, and 1.5% for X25). The lack of abnormal repeat expansions in the majority of ataxis patients tested suggests that the molecular defects associated with most ataxia cases are currently undetermined and that this population includes both familial and sporadic cases. In contrast, of the patients submitted for genetic testing for Friedrich's ataxia (FRDA), 44% (69/157) showed at least one expansion in the X25 gene, indicating that FRDA accounts for a significant proportion of the recessively inherited ataxias and appears to have a high rate of accurate clinical diagnosis. On the basis of our DNA studies, we propose a comprehensive and efficient approach for molecular analysis of ataxia patients.

Ashkenazi Jewish population frequency of the Bloom syndrome gene 2281 delta 6ins7 mutation

Bloom syndrome is an autosomal recessive disorder characterized clinically by small size, sun-sensitive facial erythema, and immunodeficiency, and cytogenetically by increased chromosome breakage and sister chromatid exchange. Genomic instability renders Bloom syndrome patients at elevated risk for multiple cancers. Bloom syndrome occurs most commonly in the Ashkenazi Jewish population due to an apparent founder effect. The BLM gene on chromosome 15q26.1 was identified to encode a RecQ DNA helicase. Multiple mutations were identified, with Ashkenazi Jewish Bloom syndrome patients almost exclusively homozygous for a complex frameshift mutation (6-bp deletion/7-bp insertion at BLM nucleotide 2,281). This molecular genetic study seeks to verify the Ashkenazi Jewish carrier frequency of the BLM 2281 delta 6ins7 allele using semiautomated allele-specific oligonucleotide (ASO) analysis. Anonymized DNA samples from 1,016 Ashkenazi Jewish individuals and 307 non-Jewish individuals were screened. Ten Ashkenazi heterozygote carriers for the 2281 delta 6ins7 mutation were identified, giving a carrier frequency estimate of 0.98%, or approximately 1 carrier out of 102 individuals in the Ashkenazi Jewish population. These results are consistent with previous estimates, and combining our findings with the published molecular data collectively yields an Ashkenazi Jewish carrier frequency of approximately 1 in 104. Given its high population frequency and detection rate among Ashkenazi Jewish patients, the blmAsh mutation constitutes an appropriate addition to screening panels for Ashkenazi Jewish disease testing.

Psychological and behavioral factors associated with colorectal cancer screening among Ashkenazim

BACKGROUND

Psychological and behavioral factors related to annual colorectal cancer (CRC) screening were examined in a sample of Ashkenazi Jewish individuals. Identification of factors related to regular CRC screening in this population is important because of the possibility of a heightened incidence of CRC.

METHODS

Eligible participants were 171 Ashkenazi Jewish adults 40 years or older attending an educational program about breast cancer genetics. Compliance with recommended guidelines for digital rectal examination and fecal occult blood test in the past year were dependent measures. Demographic variables, family history of CRC, perceived risk, physician recommendation, and worry about cancer were independent measures.

RESULTS

Digital rectal examinations and fecal occult blood tests had been obtained in the past year by 46 and 31% of the participants, respectively. A logistic regression showed that physician recommendation was related significantly to obtaining digital rectal examinations. Physician recommendation and education were related significantly to obtaining fecal occult blood tests. Although participants with family histories of CRC perceived themselves as being at increased risk of developing CRC, and were more worried about developing colon cancer, they were no more likely to adhere to CRC screening guidelines than those without such histories.

CONCLUSIONS

Overall, compliance with recommended CRC screening was low even among high-risk individuals. Physicians play a key role in motivating people to comply with CRC screening. Physicians need to en courage all asymptomatic patients 50 years and older to be screened for CRC.

Fragile X syndrome and an isodicentric X chromosome in a woman with multiple anomalies, developmental delay, and normal pubertal development

We report on an individual with developmental delays, short stature, skeletal abnormalities, normal pubertal development, expansion of the fragile X triplet repeat, as well as an isodicentric X chromosome. S is a 19-year-old woman who presented for evaluation of developmental delay. Pregnancy was complicated by a threatened miscarriage. She was a healthy child with intellectual impairment noted in infancy. Although she had global delays, speech was noted to be disproportionately delayed with few words until age 3.5 years. Facial appearance was consistent with fragile X syndrome. Age of onset of menses was 11 years with normal breast development. A maternal male second cousin had been identified with fragile X syndrome based on DNA studies. The mother of this child (S's maternal first cousin) and the grandfather (S's maternal uncle) were both intellectually normal but were identified as carrying triplet expansions in the premutation range. S's mother had some school difficulties but was not identified as having global delays. Molecular analysis of S's fragile X alleles noted an expansion of more than 400 CGG repeats in one allele. Routine cytogenetic studies of peripheral blood noted the presence of an isodicentric X in 81of 86 cells scored. Five of 86 cells were noted to be 45,X. Cytogenetic fra(X) studies from peripheral blood showed that the structurally normal chromosome had the fragile site in approximately 16% of the cells. Analysis of maternal fragile X alleles identified an allele with an expansion to approximately 110 repeats. FMRP studies detected the expression of the protein in 24% of cells studied. To our knowledge, this is the first patient reported with an isodicentric X and fragile X syndrome. Whereas her clinical phenotype is suggestive of fragile X syndrome, her skeletal abnormalities may represent the presence of the isodicentric X. Treatment of S with 20 mg/day of Prozac improved her behavior. In the climate of cost con trol, this individual reinforces the recommendation of obtaining chromosomes on individuals with developmental delay even with a family history of fragile X syndrome.

Psychological impact of receiving negative BRCA1 mutation test results in Ashkenazim

PURPOSE

Most DNA test results for breast/ovarian cancer susceptibility are negative. Because negative test results might be interpreted incorrectly and may have serious psychological and behavioral implications, determining the psychological impact of such results is important.

METHODS

A community-based sample of 289 Ashkenazim was tested for 185delAG. The 199 mutation-negatives provided data at baseline and follow-up. Increased risk participants included those who received negative test results but remained at increased risk because positive family and/or personal histories of breast or ovarian cancer made the results uninformative. Average risk meant those who tested negative and had negative family and personal histories of breast or ovarian cancer. Using a logistic regression analysis, both groups' psychological distress levels were compared at baseline and at 1 and 6 months after notification of DNA test results.

RESULTS

A logistic regression analysis showed significant but small differences in cancer-specific distress after 6 months between increased and average risk participants (P < 0.006). Increased risk participants reported more distress than average risk. General distress declined among all participants after 1 month. Although baseline and follow-up differences in cancer-specific distress obtained by the increased and average risk participants were statistically significant, none of the absolute levels observed reflected especially high degrees of stress.

CONCLUSIONS

Receipt of negative DNA test results does not have a deleterious psychological impact, whether results are informative or uninformative.

The identification of markers segregating with resistance to Schistosoma mansoni infection in the snail Biomphalaria glabrata

Both snail and parasite genes determine the susceptibility of the snail Biomphalaria glabrata to infection with the trematode Schistosoma mansoni. To identify molecular markers associated with resistance to the parasite in the snail host, we performed genetic crosses between parasite-resistant and -susceptible isogenic snails. Because resistance to infection in adult snails is controlled by a single locus, DNA samples from individual F2 and F1 backcross progeny, segregating for either the resistant or susceptible phenotypes, were pooled (bulked segregant). Genotypes for both parents were determined with 205 arbitrary decamer primers by random amplified polymorphic DNA-PCR. Of the 205 primers, 144 were informative, and the relative allele frequencies between the pools for these primers were determined. Two primers, OPM-04 and OPZ-11, produced fragments in the resistant parent of one cross that were inherited in a dominant fashion in the resistant F2 and backcross-bulked segregant progeny. Subsequent typing of DNA samples of individual progeny snails showed that the 1.2-kb marker amplified by primer OPM-04 and the 1.0-kb marker produced by primer OPZ-11 segregated in the same dominant fashion with the resistant phenotype. Sequence analysis of the 1.2-kb marker showed that it corresponds to a repetitive sequence in the snail genome with no homology to existing DNA sequences in the public databases. Analysis of the 1. 0-kb marker showed that it also corresponds to a repetitive sequence in the B. glabrata genome that contains an imperfect ORF, with homology to retrovirus-related group-specific antigens (gag) polyprotein.

Relative stability of a minimal CTG repeat expansion in a large kindred with myotonic dystrophy

The genetic basis for myotonic dystrophy (DM) is a CTG trinucleotide repeat expansion. The number of CTG repeats commonly increases in affected individuals of successive generations, in association with anticipation. We identified a large DM family in which multiple members had minimal CTG repeat expansions, and in which the number of CTG repeats remained in the minimally expanded range through at least three, and possibly four, generations. This relative stability of minimal CTG repeat expansions may help to maintain the DM mutation in the population.

Congenital myotonic dystrophy pathology and somatic mosaicism

We present the pathology and molecular genetic analysis of an infant with congenital myotonic dystrophy. The proband/infant, born at 35 weeks' gestational age to a mother with myotonic dystrophy and 750 CTG repeats, was markedly hypotonic and had severe cardiomyopathy. She died after 16 days of life. At autopsy, skeletal and heart muscles were immature and had a decrease in contractile elements. DNA CTG trinucleotide repeat analysis of the proband demonstrated 2,480 repeats in blood and a slightly greater number of repeats in skeletal muscles, viscera, and gray matter. Corresponding to the clinical course and pathology, cardiac tissues displayed somatic mosaicism, with repeats ranging from 2,760 to 3,220.

Prenatal diagnosis of a fetus with a homologous Robertsonian translocation of chromosomes 15

We present a prenatal diagnosis of a de novo homologous Robertsonian translocation involving both chromosomes 15. Amniocentesis was performed on a 36-year-old woman at 16.5 weeks of gestation. Chromosome analysis documented a 45,XX,der(15;15) (q10;q10) chromosome pattern. No evidence of a deletion was observed by FISH using a SNRPN DNA probe associated with the Prader-Willi/Angelman syndrome critical region. Molecular studies in the family using six polymorphic markers for chromosome 15 and Southern blot analysis of DNA methylation for the CpG island near the SNRPN gene showed normal biparental inheritance of chromosome 15, excluding uniparental disomy. The patient was counseled that her child would not be able to bear off-spring without clinical assistance. Otherwise the health and intellect of her child were not expected to be affected by the translocation. We consider this to be the first prenatal case identified with a balanced der(15;15)(q10;q10) Robertsonian translocation and a phenotypically normal female outcome. Prenatally identified cases of der(15;15)(q10;q10) warrant further investigation by molecular methodology.

A laboratory-based approach to biological control of snails

Development of Schistosoma mansoni in the intermediate host Biomphalaria glabrata is influenced by a number of parasite and snail genes. Understanding the genetics involved in this complex host/ parasite relationship may lead to an often discussed approach of introducing resistant B. glabrata into the field as a means of biological control for the parasite. For the snail, juvenile susceptibility to the parasite is controlled by at least four genes, whereas one gene seems to be responsible for adult nonsusceptibility. Obtaining DNA from F2 progeny snails from crosses between parasite-resistant and -susceptible snails, we have searched for molecular markers that show linkage to either the resistant or susceptible phenotype. Both restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) approaches have been used. To date, using a variety of snail and heterologous species probes, no RFLP marker has been found that segregates with either the resistant or susceptible phenotype in F2 progeny snails. More promising results however have been found with the RAPD approach, where a 1.3 kb marker appears in nearly all resistant progeny, and a 1.1 kb marker appears in all susceptible progeny.

DMD-specific FISH probes are diagnostically useful in the detection of female carriers of DMD gene deletions

The challenge of Duchenne muscular dystrophy (DMD) carrier identification resides in the ability to identify the presence of a mutant gene over the background contributed by the normal allele. Current diagnosis of carrier status when a deletion has been identified in a proband is based on an analysis of a gene dosage. We present a diagnostic strategy that uses fluorescence in situ hybridization (FISH) to detect female carriers with major deletions in the dystrophin gene. We screened a human X-chromosome-derived genomic library with a full-length dystrophin cDNA and isolated 15 dystrophin-specific cosmids that contain DMD gene exons. Six cosmids were further tested as FISH probes in control individuals and subsequently applied on chromosomes from eight males with DMD and known deletions and on samples from three female carriers. As expected, X chromosomes in normal females displayed four signals, two for the DMD-specific probe and two for the X-chromosome centromeric probe. Hybridization on chromosomal spreads from carriers of deletions revealed only one signal from the DMD-specific probe and two from the control centromeric probe. Males carrying deletions showed no DMD-specific signal for the deleted exons tested. Our data indicate that FISH could represent an alternative method for the detection of female carriers with DMD gene deletions.

Screening for 185delAG in the Ashkenazim

A study was initiated to assess interest, educational effectiveness, and implications of genetic testing for the common BRCA1 mutation, 185delAG, in the Ashkenazim. Of 333 individuals who attended group sessions, 309 (92%) participated in the study. Participants were categorized as having negative family history (67%), positive family history (defined, by a relaxed criterion, as one first-degree relative or two second-degree relatives with breast [premenopausal] or ovarian cancer) (22%), positive personal history (7%), and both positive personal history and positive family history (4%). Group education was effective, as shown by the improvement in participant scores from pre- to posteducation tests. For the 289 individuals (94%) who requested testing, the major reasons included concern for their own risk, concern for the risk of their children, and desire to learn about surveillance options. The most common reason given by participants who declined testing was concern about health insurance. Six participants found to be heterozygous for the 185delAG mutation received results and were offered genetic counseling. Participants had consented for additional testing without receiving results and were screened for the 6174delT mutation in BRCA2, and seven were found to be positive. All identified carriers reported at least one first- or second-degree relative with a history of breast or ovarian cancer, although they did not all meet our study criteria for positive family history. Given these outcomes, we conclude that screening for breast and ovarian cancer susceptibility is most appropriate for individuals with a positive personal or positive family cancer history. We propose a guideline for future studies designed to identify individuals who may benefit from genetic testing for inherited breast and ovarian cancer.

Southern analysis for detection of CAG repeat expansions associated with dentatorubral pallidoluysian atrophy

Dentatorubral pallidoluysian atrophy (DRPLA) is an autosomal dominant neurodegenerative disorder caused by expansion of an unstable, tandemly repeated trinucleotide sequence, (CAG)n, in a novel gene on human chromosome 12p12-pter. Molecular diagnosis of DRPLA uses the polymerase chain reaction (PCR) to amplify and characterize the number of CAG repeats carried by individuals. The PCR analysis is fairly straightforward when two alleles are identified. However, when only a single allele is observed, it is difficult to know whether the sample is homozygous or whether there was failure to amplify the second allele. We describe a Southern analysis for detection of the DRPLA CAG repeat, providing an independent method for the assessment of expanded alleles.

Molecular detection of new mutations, resolution of ambiguous results and complex genetic counseling issues in Huntington disease

Huntington disease (HD) is an autosomal dominant neurodegenerative disorder caused by expansion of a variable length (CAG)n repeat in the 5' coding region of a novel gene on chromosome 4p16.3. We provide comprehensive molecular analysis of a sporadic case of HD in which a paternally derived normal length allele expanded to an affected length allele. Linkage analysis and paternity testing confirm the paternal origin of the expansion and demonstrate that unequal crossing over during meiosis is an unlikely mechanism for de novo expansion in HD. This case identifies a complex genetic counseling issue for the families of sporadic cases since calculations of recurrence risk are not possible at this time. In addition, we describe utilization of a combination of polymerase chain reaction (PCR) based assays for examination of both the CAG repeat and an adjacent variable length CCG repeat in the huntingtin gene. The combination of these assays can increase the accuracy of molecular diagnosis for HD and may clarify any ambiguous results obtained during molecular testing of HD families.

Ashkenazi Jewish population frequencies for common mutations in BRCA1 and BRCA2

BRCA1 and BRCA2 are the two major identified causes of inherited breast cancer, with mutations in either gene conferring up to 80-90% lifetime risk of breast cancer in carrier females. Mutations in BRCA1 account for approximately 45% of familial breast cancer and 90% of inherited breast/ovarian cancer, whereas mutations in BRCA2 account for a comparable percentage of inherited breast cancer cases. Over 85 distinct BRCA1 mutations and a growing list of BRCA2 mutations have been identified, with the majority resulting in protein truncation. A specific BRCA1 mutation, 185delAG, has a reported increased carrier frequency of approximately 0.9% in the Ashkenazi Jewish population, but is also found in rare non-Jewish patients with a different haplotype. The 6174delT mutation in BRCA2 was recently identified as a frequent mutation in 8 out of 107 Ashkenazi Jewish women diagnosed with breast cancer by age 50 (ref. 8), as well as in three Ashkenazi male breast cancer patients. We have conducted a large-scale population study to investigate the prevalence of specific BRCA1 and BRCA2 mutations in Ashkenazi Jewish individuals who were unselected for breast cancer. BRCA1 mutation screening on approximately 3,000 Ashkenazi Jewish samples determined a carrier frequency of 1.09% for the 185delAG mutation and 0.13% for the 5382insC mutation. BRCA2 analysis on 3,085 individuals from the same population showed a carrier frequency of 1.52% for the 6174delT mutation. This expanded population-based study confirms that the BRCA1 185delAG mutation and the BRCA2 6174delT mutation constitute the two most frequent mutation alleles predisposing to hereditary breast cancer among the Ashkenazim, and suggests a relatively lower penetrance for the 6174delT mutation in BRCA2.

Relevance of RET proto-oncogene mutations in sporadic medullary thyroid carcinoma

Analysis of peripheral blood or tumor DNA samples from 101 patients with apparent sporadic medullary thyroid carcinoma (MTC) was performed to assess the frequency of RET proto-oncogene mutations in this patient population. Peripheral blood and/or tumor DNA was amplified by polymerase chain reaction. DNA sequence or restriction enzyme analysis was performed to detect mutations of RET proto-oncogene codons 609, 611, 618, 620, 634, 768, and 918. Six of 101 patients with apparent sporadic MTC had peripheral blood DNA mutations more commonly associated with hereditary MTC. In 4 patients, these mutations led to the identification of previously unrecognized kindreds. The remaining 2 patients were examples of de novo mutations. A codon 918 mutation was found in 14 of 57 (approximately 25%) tumor DNA samples. Mutations were not identified in the remaining patients. In this large cancer center population, approximately 6% of patients with sporadic MTC carry peripheral blood DNA mutations, either inherited or de novo, more commonly associated with MEN 2A or familial MTC. Seven additional gene carriers were identified as a direct result of these studies, a 2-fold multiplying effect. We conclude routine application of RET proto-oncogene testing should be included in all cases of apparent sporadic MTC.

Use of RAPD-PCR to differentiate genetically defined lines of an intermediate host of Schistosoma mansoni, Biomphalaria glabrata

The genetic differentiation among several laboratory-maintained pedigree snail lines of Biomphalaria glabrata (with different susceptibility phenotypes to Schistosoma mansoni infection) was assessed with the random amplified polymorphic DNA method. Out of the 20 primers tested, 2 (OPA-01 and OPA-06) gave reproducible markers with either individual or bulked DNA samples from resistant (BS-90, 10-R2, LAC-line) and susceptible (M-line) snails. Arbitrary primer, OPA-01, amplification of BS-90 DNA identified a 180-bp strain-specific fragment and a 400-bp marker in the susceptible M-line stock. In the 10-R2 and LAC snail lines, OPA-01 specific markers of 200 bp and 550 bp were identified. Amplification with primer OPA-06 identified several major strain-specific markers in the BS-90 (150 bp, 400 bp, 800 bp) and M-line (1,100 bp) snails. The heritability of the RAPD markers was evaluated in progeny snails derived from a cross between the BS-90 and M-line stocks. Results showed that markers were inherited in a dominant or codominant fashion. The 1,100-bp M-line marker was inherited in all susceptible progeny snails analyzed.

Pharmacokinetics of reconstituted human high-density lipoprotein in pigs after hemorrhagic shock with resuscitation

OBJECTIVES

Reconstituted human high-density lipoprotein (HDL) can inhibit lipopolysaccharide effects in vivo. The major objectives of this study were to characterize the pharmacokinetics of reconstituted HDL in a stressed large-animal model and to provide preclinical tolerance information in support of use of reconstituted HDL in humans.

DESIGN

A randomized, blinded, placebo-controlled trial where each animal received either reconstituted human HDL at a dose of 100 mg/kg (apolipoprotein A-I) or placebo, immediately after hemorrhagic shock and resuscitation.

SETTING

Animal laboratory.

SUBJECTS

Twelve immature female swine (18 to 25 kg) were studied.

INTERVENTIONS

Six to 8 days before shock and study drug administration, animals were anesthesized and catheters were placed in the external jugular vein and abdominal aorta. These catheters were secured to the dorsal surface. On the day of shock, the animals were sedated (alpha-chloralose) and 50 mL/kg of arterial blood was removed over 0.5 hr. One half hour after blood removal, shed blood was infused, which was immediately followed by study drug (reconstituted HDL or placebo), and then by 1 L of lactated Ringer's solution.

MEASUREMENTS AND MAIN RESULTS

Physiologic (arterial blood pressure, heart rate, respiratory rate) and laboratory (serum chemistries, hematologic and coagulation studies, and blood gases) measurements were determined intermittently for 96 hrs after the induction of shock. Blood was collected intermittently for 48 hrs after shock for assay of apolipoprotein A-I and phosphatidylcholine in plasma. Reconstituted HDL was well tolerated and did not appear to alter the physiologic responses to shock and resuscitation. HDL transient increase in aspartate aminotransferase concentration was noted in the reconstituted group but this increase normalized by 24 hrs after drug administration. Mean apolipoprotein A-I pharmacokinetic parameters were as follows: half-life 24.5+/-5.3 (SD) hrs; clearance 41.9+/-10 mL/hr; and volume of distribution 1.39+/-0.08 L. The apparent mean half-life of phosphatidylcholine was 5.4+/-0.8 hrs.

CONCLUSIONS

Reconstituted human HDL was well tolerated in animals that had undergone hemorrhagic shock with resuscitation. The apolipoprotein component of reconstituted HDL had a relatively long half-life, with distribution limited to the vascular space. These findings support the investigational use of this product in humans.

Population-specific screening by mutation analysis for diseases frequent in Ashkenazi Jews

We describe a partially automated DNA mutation assay for detecting the most frequent mutations in the alpha-subunit of beta-hexosaminidase A, the acid beta-glucosidase and the cystic fibrosis transmembrane conductance regulator genes for the Ashkenazi Jewish population. The assay detects carriers for Tay-Sachs disease, Gaucher disease, and cystic fibrosis with sensitivities of at least 92%, 96%, and 97%, respectively. Among 1,364 young adults of Ashkenazic ancestry in the Dor Yeshurim community who were tested, 52 were Tay-Sachs carriers, 110 were Gaucher carriers, and 62 were cystic fibrosis carriers. Ten individuals were carriers for two diseases, and three unsuspected cases were diagnosed with Gaucher disease based on mutation test results. In addition to Tay-Sachs mutation data, results for hexosaminidase A activity were also available. All of 1,254 samples normal by enzyme quantitation were also negative for the three alpha-subunit mutations tested, and all of 43 samples with 'inconclusive' enzyme results were negative by DNA. Only 52 of 67 samples positive by enzyme assay were also positive for one of the three mutations tested for Tay-Sachs disease. The data suggest a high degree of false positivity inherent in enzyme identification of carriers. There are no correlative methods to assess the sensitivity of Gaucher and CF carrier testing. The results show that population screening can be carried out efficiently by DNA analysis, with the accrual of carrier information for three separate diseases conducted as a single test. Furthermore, the DNA method for Tay-Sachs screening appears to exceed the specificity of hexosaminidase A enzyme testing.

Epstein-Barr virus-associated leiomyosarcomas in liver transplantation recipients. Origin from either donor or recipient tissue

BACKGROUND

Leiomyosarcoma, a mesenchymal malignancy with smooth muscle differentiation, is extremely rare in children. Immunosuppression, due to either antirejection medication in organ transplantation recipients or human immunodeficiency virus infection (HIV), appears to constitute a predisposition.

METHODS

Two cases of leiomyosarcoma in pediatric liver transplantation recipients were investigated and compared clinically with respect to site of origin and course of the disease and pathologically by routine histology and electron microscopy, by forensic DNA methodology for origin from donor or recipient tissue, and by EBER-1 in situ hybridization for evidence of latent Epstein-Barr virus (EBV) infection.

RESULTS

A 9-year-old male developed a high grade, poorly differentiated leiomyosarcoma in his allografted liver 2 years after transplantation, and despite antineoplastic chemotherapy, he died of metastatic disease. The genotype of his tumor indicated an origin from allografted tissue. A 12-year-old female had a low grade retroperitoneal leiomyosarcoma involving the superior mesenteric vein. After resection, she remained disease free without chemotherapy. The genotype of her tumor indicated an origin from native tissue. In both tumors, latent EBV infection was documented.

CONCLUSIONS

Neoplastic smooth muscle proliferation in immunosuppressed liver transplantation recipients is analogous to the more common posttransplantation lymphoproliferative disorder in involving transformation of either engrafted donor tissue or recipient tissue elsewhere in the body, in displaying a wide spectrum of histologic differentiation, grade and clinical behavior, and in exhibiting evidence of latent EBV infection.

Somatic heterogeneity of the CTG repeat in myotonic dystrophy is age and size dependent

The most common form of adult muscular dystrophy, myotonic dystrophy (DM), is caused by the abnormal expansion of the CTG repeat, located in the 3' UTR of the DM gene. The expanded-CTG allele often presents as a diffused band on Southern blot analysis, suggesting somatic mosaicism. In order to study the somatic instability of the CTG repeat, we have investigated the dynamics of the size heterogeneity of the CTG expansion. Size heterogeneity is shown as a smear on Southern blot and is measured by the midpeak-width ratio of the expanded allele to the normal sized allele. The ratio is also corrected for compression in the higher-molecular-weight region. It is found that the size heterogeneity of the expanded-CTG repeats, of 173 DM patients, correlates well with the age of the patient (r = .81, P << .001). The older patients show larger size variation. This correlation is independent of the sex of either the patient or the transmitting parent. The size heterogeneity of the expansion, based on age groups, is also dependent on the size of the expanded trinucleotide repeat. However, obvious size heterogeneity is not observed in congenital cases, regardless of the size of expansion. Comparison of individual patient samples collected at two different times has confirmed that the degree of size heterogeneity increases with age and has revealed a subtle but definite upward shift in the size of the expanded-CTG allele. The progression of the CTG repeat toward larger expansion with age is further confirmed by small-pool PCR assay that resolved the heterogeneous fragments into discrete bands.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation of a GCC repeat showing expansion in FRAXF, a fragile site distal to FRAXA and FRAXE

Three folate-sensitive fragile sites, termed FRAXA, FRAXE and FRAXF, have been identified on the distal end of chromosome Xq. The first two contain expanded, hypermethylated and unstable CGG (or GCC) repeats within CpG islands. We now report the isolation of similar sequences responsible for the third fragile site, FRAXF. A 5-kilobase EcoRI fragment derived from a cosmid coincident with the cytogenetic anomaly detects expanded, methylated and unstable sequences in five individuals who exhibit fragile sites in distal Xq; these individuals have normal repeat lengths at both FRAXA and FRAXE. By sequence analysis, the expanded region contains a GCC repeat. PCR and sequence analysis of chromosomes from the general population indicates that the repeat is polymorphic (6 to 29 triplets), and is stable upon transmission.

Length of uninterrupted CGG repeats determines instability in the FMR1 gene

Analysis of 84 human X chromosomes for the presence of interrupting AGG trinucleotides within the CGG repeat tract of the FMR1 gene revealed that most alleles possess two interspersed AGGs and that the longest tract of uninterrupted CGG repeats is usually found at the 3' end. Variation in the length of the repeat appears polar. Alleles containing between 34 and 55 repeats, with documented unstable transmissions, were shown to have lost one or both AGG interruptions. These comparisons define an instability threshold of 34-38 uninterrupted CGG repeats. Analysis of premutation alleles in Fragile X syndrome carriers reveals that 70% of these alleles contain a single AGG interruption. These data suggest that the loss of an AGG is an important mutational event in the generation of unstable alleles predisposed to the Fragile X syndrome.

Schistosoma mansoni: relationship between low fecundity and reduced susceptibility to parasite infection in the snail Biomphalaria glabrata

Biomphalaria glabrata snails which were not susceptible as juveniles to infection by Schistosoma mansoni were selectively bred (by self-fertilization) from the highly susceptible NMRI laboratory snail stock. The susceptibility rate among juvenile snails derived from interbreeding NMRI parents was initially 85-95%, but after several generations of selection, less than 5% of exposed snails became infected by the parasite. Selection for low susceptibility also resulted in a large proportion of snails that displayed low fecundity and produced abnormal egg masses. Individual adult snails which were isolated from an interbreeding population of nonselected NMRI snails usually produced well-developed egg masses each containing 15-30 embryos. However, when juvenile snails from this same population were reared in isolation and not allowed to cross-fertilize, many displayed a pattern of low fecundity and abnormal egg production similar to that observed in the selected low susceptible line. Furthermore, it was found that many of the isolated snails which exhibited low egg production were also not susceptible to parasitic infection.

CAG repeat size and clinical presentation in Huntington's disease

The specific mutation in Huntington's disease (HD) is an expansion of the unstable CAG trinucleotide repeat in the IT15 gene in chromosome 4p. We examined the relationship between the CAG repeat size and clinical presentation in 36 patients with suspected diagnosis of HD. Twelve patients had no relatives with documented HD, and five of them failed to show the expanded (>37) CAG repeats. The remaining 31 patients, including seven patients with atypical clinical features for HD (three without and four with family history of documented HD), were heterozygotes for the CAG repeat expansion. There were large CAG repeats (50 copies) in paternally transmitted HD cases with early onset (age 30 or earlier). The rate of disease progression was faster in paternally transmitted cases regardless of the CAG repeat length or age of onset. We conclude that (1) patients lacking the family history of HD frequently show no expansion of the CAG repeats, and (2) the sex of the affected parent influences both the CAG repeat size and the phenotypic expression of the HD gene in the offspring.

Stress and unaided smoking cessation: a prospective investigation

A prospective design was used to determine the outcomes associated with unaided smoking cessation and the influence of stress on cessation. Heavy smokers (N = 308) completed stress-related measures and were then recontacted at 1, 6, and 12 months. At each follow-up, they indicated their smoking status (which was confirmed by collateral report and biochemical tests) and completed several stress-related questionnaires. Results indicated that 33% of subjects smoked continuously throughout the year, 39% quit briefly but subsequently relapsed, and 15% quit (confirmed biochemically). An additional 7% reported that they had quit, but this could not be confirmed, and 6% were lost to follow-up. Compared with nonquiters, quitters reported less perceived stress, greater self-efficacy, greater use of problem solving and cognitive restructuring, and less reliance on wishful thinking, self-criticism, and social withdrawal. A model to forecast quitting was built and cross-validated.

Experience of an academic reference laboratory using automation for analysis of cystic fibrosis mutations

OBJECTIVE

To examine the use of partial automation for molecular analysis of cystic fibrosis and to evaluate the diagnostic experience gained.

DESIGN

Twenty-four cystic fibrosis mutations, with cumulative mutation detection of 89% in North American whites and of 97% in the Ashkenazim, were tested by multiplex amplification and allele-specific oligonucleotide hybridization.

SETTING

A university-based DNA diagnostic laboratory.

SUBJECTS

More than 700 serial specimens were analyzed for cystic fibrosis mutations over a 5-month period. The study included 377 individuals tested for carrier status, of which 288 had no family history for cystic fibrosis; prenatal diagnosis for 17 fetuses at a one in four risk and eight pregnancies at lower risk; fetal or parental samples for 33 pregnancies with fetal ultrasound abnormalities; 40 individuals diagnosed with cystic fibrosis; and 87 individuals with a possible diagnosis of the disease.

RESULTS

Automation has permitted increasing numbers of mutations while decreasing personnel time and cost. Mutation testing identified 10 carriers with no family history for cystic fibrosis, four couples at a one in four risk, and five affected fetuses, one ascertained by abnormal fetal ultrasound. Mutation analysis also identified two mutant copies of the gene in 26 of 40 individuals with a clinical diagnosis of cystic fibrosis, and in two of 87 patients with possible cystic fibrosis.

CONCLUSION

This partially automated, direct mutation analysis provides DNA diagnostic laboratories with the capacity to process a larger number of samples at lower cost with greater sensitivity for mutation detection. As pilot screening programs are reported, it is appropriate to reevaluate recommendations regarding population-based carrier screening for cystic fibrosis.

A robotics-assisted procedure for large scale cystic fibrosis mutation analysis

We describe a convenient, efficient, semiautomated protocol for assaying large numbers of DNA samples for over 20 mutations causing cystic fibrosis. The protocol uses the following: (1) a programmable robotic workstation to perform rapid pipetting and dot-blotting operations, (2) an allele-specific oligonucleotide hybridization in a single water bath without correcting for G+C content of oligonucleotides, and (3) a combinatorial system that allows direct determination of the genotype for more frequent mutations. We have used this system routinely for 16 months for carrier detection and for diagnosis of cystic fibrosis. The method can be readily applied to any combination of allele-specific oligonucleotide assays whether for multiple alleles at one locus or for a few alleles at multiple loci.

Effects of the sex of myotonic dystrophy patients on the unstable triplet repeat in their affected offspring

The mutation responsible for myotonic dystrophy (DM) is an unstable expansion of the CTG repeat within the myotonin protein kinase gene. To examine whether the parental origin of the expanded repeat influences the repeat size in offspring, we studied 51 father-child and 59 mother-child pairs with DM. Small expansions in fathers resulted in larger size expansions in their offspring, while large paternal expansions resulted in less size change in their offspring. However, there was no correlation between maternal size expansion and size increase in offspring for either congenital or noncongenital DM. These data suggest that the sex of the affected parent influences the unstable expansion of the repeat in DM offspring. While some evidence suggests that DNA methylation status cannot explain this observation, the mechanism for differential maternal/paternal transmission expansion is currently unknown.

Schistosoma mansoni: analysis of an unusual infection phenotype in the intermediate host snail Biomphalaria glabrata

Snails from a B. glabrata stock, selected for nonsusceptibility to the NMRI strain of S. mansoni, exhibited unusual schistosome infections, with multiple sporocysts prominent in the head-foot (foot-sporocysts). When F1 progeny from numerous crosses between well-defined susceptible (S) and resistant (R) parental snails were exposed, 60% of the infected snails also exhibited this unusual phenotype. F1 progeny from S x S snail crosses developed normal infections. Foot-sporocysts usually developed much later than secondary sporocysts of normal infections and before 12 weeks postexposure the tissue reaction surrounding foot-sporocysts was less intense than reactions to sporocysts in other tissues of the body. Cercariae were seen emerging directly from foot-sporocysts. Infection of S x R hybrid progeny by three other strains of S. mansoni also resulted in the production of foot-sporocysts. Development of the foot-sporocyst infection phenotype in progeny from many snail crosses suggests that this phenotype is more common than previously recognized. Over 50% of the F1 progeny from S x R parental crosses developed patent infections, a fact relevant to the possible biological control of schistosomiasis by the introduction of refractory snails into endemic areas.

Stress and unaided smoking cessation: a prospective investigation

A prospective design was used to determine the outcomes associated with unaided smoking cessation and the influence of stress on cessation. Heavy smokers (N = 308) completed stress-related measures and were then recontacted at 1, 6, and 12 months. At each follow-up, they indicated their smoking status (which was confirmed by collateral report and biochemical tests) and completed several stress-related questionnaires. Results indicated that 33% of subjects smoked continuously throughout the year, 39% quit briefly but subsequently relapsed, and 15% quit (confirmed biochemically). An additional 7% reported that they had quit, but this could not be confirmed, and 6% were lost to follow-up. Compared with nonquiters, quitters reported less perceived stress, greater self-efficacy, greater use of problem solving and cognitive restructuring, and less reliance on wishful thinking, self-criticism, and social withdrawal. A model to forecast quitting was built and cross-validated.

In situ hybridization shows direct evidence of skewed X inactivation in one of monozygotic twin females manifesting Duchenne muscular dystrophy

A novel combination of conventional and molecular cytogenetic techniques was used to investigate the expression of an X-linked recessive disorder in one of monozygotic (MZ) twin females. These twins carry a deletion, approximately 300 kb in length, in one of their X chromosomes within the dystrophin gene, which is responsible for Duchenne muscular dystrophy (DMD) in one twin [Richards et al.: Am J Hum Genet 46:672-681, 1990]. A unique DNA fragment generated from an exon within this gene deletion was hybridized in situ to both twins' metaphase chromosomes, a probe which would presumably hybridize only to the normal X chromosome and not to the X chromosome carrying the gene deletion. Chromosomes were identified by reverse-banding (R-banding) and by the addition of 5-bromodeoxyuridine (BrdU) in culture to distinguish early and late replicating X chromosomes, corresponding to active and inactive X chromosomes, respectively. Hybridization experiments showed predominant inactivation of the normal X chromosome in the twin with DMD. This is the first report showing direct evidence at the chromosome level of unequal inactivation of cytogenetically normal X chromosomes resulting in the manifestation of an X-linked recessive disorder in one of monozygotic twin females. This study may now facilitate other research of unequal X inactivation and of females manifesting X-linked recessive disorders.