Chemical probes and inhibitors of bromodomains outside the BET family

Significant progress has been made in discovering inhibitors and chemical probes of bromodomains, epigenetic readers of lysine acetylation.

In the last five years, the development of inhibitors of bromodomains has emerged as an area of intensive worldwide research. Emerging evidence has implicated a number of non-BET bromodomains in the onset and progression of diseases such as cancer, HIV infection and inflammation. The development and use of small molecule chemical probes has been fundamental to pre-clinical evaluation of bromodomains as targets. Recent efforts are described highlighting the development of potent, selective and cell active non-BET bromodomain inhibitors and their therapeutic potential. Over half of typical bromodomains now have reported ligands, but those with atypical binding site residues remain resistant to chemical probe discovery efforts.

Design and synthesis of potent and selective inhibitors of BRD7 and BRD9 bromodomains

We describe potent and selective inhibitors of the BRD7 and BRD9 bromodomains intended for use as chemical probes to elucidate the biological roles of BRD7 and BRD9 in cells.

The High Incidence of Reading Disability in Twin Boys and Its Implications for Genetic Analyses

In 1975 the Australian Council of Educational Research (ACER) conducted a nationwide survey of literacy and numeracy in 10- to 14-year olds. A total of 297 of the 12875 children involved were twins. By age 14, only 42% of the twin boys achieved adequate standards of literacy compared with 71% of single-born boys. The deficit in twin girls was much less and twins of both sexes were only moderately behind in numeracy. A survey of 9-13-year-old twin boys in the La Trobe Twin Study (LTS) produced similar results with 75% being below average in reading skills and 23% behind by 18 months or more, despite above average IQs. The ACER data are corroborated by teachers' reports obtained in the same survey, which indicate also how few of the twins with problems are receiving remediation and the high incidence of classroom problems in spelling and reading reversals. The pattern of mistakes twins make on specific items in the ACER survey can be explained as resulting either from specific cognitive deficits or from problems in concentration. The same factors influence performance on different tasks, so that literacy and numeracy are much more closely interrelated in twins than in singletons, and also correlate more with a measure of verbal intelligence. Implications for genetic analysis of scholastic achievement are examined, centering around the different factor structure of abilities in twins and common family environmental effects which are unique to twins.

The Role of Parental Attitudes in the Development of Temperament in Twins at Home, School and in Test Situations

In the La Trobe Twin Study, data are collected on temperament and social development in 3-15 year old twins and singletons from four different sources: questionnaires to parents covering development from birth to the present plus the Bristol Social Adjustment Guide completed by the teacher, Sattler's Behavior and Attitude Checklist completed by the tester, and the Qualitative Score on the Porteus Maze Test. Particular stresses are identified which the parents perceive as distinguishing a multiple from a singleton birth. Whereas they perceive no differences between the first and second-born in birth complications, the second-born is judged less favourably particularly in MZ pairs. The distinction continues in the later assessments by the teacher and tester, where in addition the male twins are seen as being different from other children both in cognition and in temperament. It is proposed that social and cognitive development of twins are interrelated and have two unique components, one related to the greater problems accompanying a multiple birth and the other to comparisons between cotwins.

Discovery and optimization of small-molecule ligands for the CBP/p300 bromodomains

Small-molecule inhibitors that target bromodomains outside of the bromodomain and extra-terminal (BET) sub-family are lacking. Here, we describe highly potent and selective ligands for the bromodomain module of the human lysine acetyl transferase CBP/p300, developed from a series of 5-isoxazolyl-benzimidazoles. Our starting point was a fragment hit, which was optimized into a more potent and selective lead using parallel synthesis employing Suzuki couplings, benzimidazole-forming reactions, and reductive aminations. The selectivity of the lead compound against other bromodomain family members was investigated using a thermal stability assay, which revealed some inhibition of the structurally related BET family members. To address the BET selectivity issue, X-ray crystal structures of the lead compound bound to the CREB binding protein (CBP) and the first bromodomain of BRD4 (BRD4(1)) were used to guide the design of more selective compounds. The crystal structures obtained revealed two distinct binding modes. By varying the aryl substitution pattern and developing conformationally constrained analogues, selectivity for CBP over BRD4(1) was increased. The optimized compound is highly potent (K_d = 21 nM) and selective, displaying 40-fold selectivity over BRD4(1). Cellular activity was demonstrated using fluorescence recovery after photo-bleaching (FRAP) and a p53 reporter assay. The optimized compounds are cell-active and have nanomolar affinity for CBP/p300; therefore, they should be useful in studies investigating the biological roles of CBP and p300 and to validate the CBP and p300 bromodomains as therapeutic targets.

A series of potent CREBBP bromodomain ligands reveals an induced-fit pocket stabilized by a cation-π interaction

The benzoxazinone and dihydroquinoxalinone fragments were employed as novel acetyl lysine mimics in the development of CREBBP bromodomain ligands. While the benzoxazinone series showed low affinity for the CREBBP bromodomain, expansion of the dihydroquinoxalinone series resulted in the first potent inhibitors of a bromodomain outside the BET family. Structural and computational studies reveal that an internal hydrogen bond stabilizes the protein-bound conformation of the dihydroquinoxalinone series. The side chain of this series binds in an induced-fit pocket forming a cation–π interaction with R1173 of CREBBP. The most potent compound inhibits binding of CREBBP to chromatin in U2OS cells.

Progress in the development and application of small molecule inhibitors of bromodomain-acetyl-lysine interactions

Bromodomains, protein modules that recognize and bind to acetylated lysine, are emerging as important components of cellular machinery. These acetyl-lysine (KAc) "reader" domains are part of the write-read-erase concept that has been linked with the transfer of epigenetic information. By reading KAc marks on histones, bromodomains mediate protein-protein interactions between a diverse array of partners. There has been intense activity in developing potent and selective small molecule probes that disrupt the interaction between a given bromodomain and KAc. Rapid success has been achieved with the BET family of bromodomains, and a number of potent and selective probes have been reported. These compounds have enabled linking of the BET bromodomains with diseases, including cancer and inflammation, suggesting that bromodomains are druggable targets. Herein, we review the biology of the bromodomains and discuss the SAR for the existing small molecule probes. The biology that has been enabled by these compounds is summarized.

Who should fund and control the direction of human behavior genetics? Review of Nuffield Council on Bioethics 2002 report, genetics and human behaviour: the ethical context

In this (Nuffield Council on Bioethics 2002), the third in its series on ethics and related issues in genetics (see also Nuffield Council on Bioethics 1993 and Nuffield Council on Bioethics 1998), the Nuffield Council has focused on four'normal' behaviors; intelligence, personality, antisocial behavior and sexual orientation. This is a narrow range of behaviors and one where their discussion of the potential impact of predictive genetic testing is probably inappropriate. They also take an unduly narrow view of the purposes of behavior genetics in the 21st century. It is not simply to estimate heritability but to understand more about the structure of behavior and the processes which underlie it. Their narrow focus and their negative approach to the history and achievements of genetics is reflected in their less than positive support for future behavior genetic research. Behavior geneticists need to do more to publicize what their field has achieved in order to counter the very extensive antibehavior genetics initiatives which are almost unique in science. At the same time, organizations such as the Nuffield Council need to consider carefully the impact their deliberations may have on research funding.

Genetic and environmental influences on separation anxiety disorder symptoms and their moderation by age and sex

We estimated genetic and environmental influences on mother-rated DSM-III-R separation anxiety disorder (SAD) symptoms in 2043 3 to 18-year-old male and female twin pairs and their siblings (348 pairs) recruited from the Australian NH&MRC Twin Registry. Using DeFries and Fulker's (1985) multiple regression analysis, we found that genetic and shared environmental influences both contributed appreciably to variation in SAD symptoms (h2 = .47, SE = .07; c2 = .21, SE = .05) and were significantly moderated by both sex and age. Genetic influences were greater for girls than boys (h2 = .50 and .14, respectively), whereas shared environmental influences were greater for boys than girls (c2 = .51 and .21, respectively). Genetic influences increased with age. whereas shared environmental influences decreased with age. Shared environmental influences were greater in magnitude for twins than for nontwin siblings (c2 = .28 versus .13, respectively). Implications of these findings for theories of the cause of separation anxiety are discussed.

Phenotypic and genetic analyses of a short measure of psychosis-proneness in a large-scale Australian twin study

Previous genetic analyses of psychosis proneness have been limited by their small sample size. For the purposes of large-scale screening, a 12-item questionnaire was developed through a two-stage process of reduction from the full Chapman and Chapman scales. 3685 individuals (including 1438 complete twin pairs) aged 18-25 years and enrolled in the volunteer Australian Twin Registry returned a mail questionnaire which included this psychosis proneness scale and the Eysenck Personality Questionnaire. Despite the brevity of the questionnaire, item and factor analysis identified four unambiguous and essentially uncorrelated scales. There were (1) Perceptual Aberration--Magical Ideation; (2) Hypomania--Impulsivity/Nonconformity; (3) Social Anhedonia and (4) Physical Anhedonia. Model-fitting analyses showed additive genetic and specific environmental factors were sufficient for three of the four scales, with the Social Anhedonia scale requiring also a parameter for genetic dominance. There was no evidence for the previously hypothesised sex differences in the genetic determination of psychosis-proneness. The potential value of multivariate genetic analysis to examine the relationship between these four scales and dimensions of personality is discussed. The growing body of longitudinal evidence on psychosis-proneness suggests the value of incorporating this brief measure into developmental twin studies.

A multivariate regression analysis of adolescent multiple drug use in two western Canadian provinces

This article reports on the results of a multiple regression analysis of an adolescent multiple drug use index on 17 predictor variables from the PRIDE CANADA Drug survey with 18,685 Grades 9 through 12 students in two Western Canadian provinces in 1995-96. The predictor variables represent eight familial, five school and peer, and four individual level attributes and behaviours. The regression analysis is used to estimate the combined effects along with the relative importance of the predictor variables on the students' self-reported use of 11 drugs combined into a multiple drug use index. Separate analyses are conducted for the male and female students. The results indicate that two of the most important predictor variables are the frequency with which both the female and male students report getting into trouble at school and the frequency of the students' participation in worship. The relative importance of these two variables and other variables in relation to the students' multiple use of drugs differ to some extent for the two genders.

Prophylactic scleral buckle for prevention of retinal detachment following vitrectomy for macular hole

AIM

To review the rate of retinal detachment after macular hole surgery in patients who received vitrectomy and scleral buckle versus those who had vitrectomy alone.

METHODS

All patient charts and hospital records were examined for patients who underwent vitrectomy surgery for macular hole between September 1993 and June 1997. A total of 326 patients were identified and all were followed for a minimum of 6 months. Clinical records were examined for details of the surgical procedure, visual acuity, hole closure status, adjuvant therapies used, and postoperative retinal attachment status. Relative risks (the ratio of the incidence rate in the exposed to that in the unexposed) with 95% confidence intervals and chi(2) tests were calculated to determine which variables were associated with retinal detachment. The primary outcome measure in this review was retinal attachment status.

RESULTS

Of 326 eyes which underwent surgery for macular hole during the study period, scleral buckles were utilised in 152 (46.6%) patients. Analysis revealed a detachment rate of 13.2% in patients who did not receive a scleral buckle compared with 5.9% detachment rate in those who did. Analysis of these results indicated a 2.42 times greater risk of developing a retinal detachment in patients without a scleral buckle. Complications related to the use of scleral buckles occurred in two of 152 cases (1.3%)

CONCLUSIONS

A reduction in the rate of retinal detachment was noted in patients receiving prophylactic scleral buckles. Those finding suggest a possible beneficial effect of this adjunctive procedure in preventing postoperative retinal detachments. The authors are currently preparing a multicentred, prospective, clinical trial to further study this hypothesis

Motor coordination and kinaesthesis in boys with attention deficit-hyperactivity disorder

In the current study, movement ability and underlying kinaesthetic processes of boys with attention deficit-hyperactivity disorder (ADHD) were compared with a group of control children. Two groups of 16 boys with either predominantly inattentive subtype ADHD (ADHD-PI) or combined subtype ADHD (ADHD-C) were compared with 16 control boys matched on age and verbal IQ. The findings demonstrated that the children with ADHD had significantly poorer movement ability than the control children. A high percentage of children with ADHD displayed movement difficulties consistent with developmental coordination disorder. In addition, the current study found that the type and degree of movement difficulty differed between subtypes. Children with ADHD-PI had significantly poorer fine motor skill while children with ADHD-C were found to experience significantly greater difficulty with gross motor skill. The severity of the children's inattentive symptomatology was found to be a significant predictor of motor coordination difficulties. Kinaesthetic sensitivity was not found to differ significantly between the groups.

Synthesis and biological evaluation of cryptophycin analogs with substitution at C-6 (fragment C region)

Analogs of the antitumor agents cryptophycins 1 and 8 with dialkyl substitution at C-6 (fragment C) were synthesized and evaluated for in vitro cytotoxicity against human leukemia cells (CCRF-CEM). The activity of these analogs decreased as the size of the substituents at C-6 increased. The C-6 spirocylopropyl compound (2g) was highly potent in vitro and showed excellent antitumor activity in animal models.

Functional brain electrical activity mapping in boys with attention-deficit/hyperactivity disorder

BACKGROUND

Symptoms of attention-deficit/hyperactivity disorder (ADHD) have been associated with frontal lobe deficits. We used a novel brain electrical imaging method to investigate rapid and continuous changes in brain activity during the continuous performance task (CPT) in normal boys and in boys with ADHD. The amplitude and latency topography of the steady-state visually evoked potential (SSVEP) were examined while subjects performed the "X" version of the CPT (CPT-X; the reference task) and the "A-X" version of the CPT (CPT-AX).

METHODS

Seventeen boys meeting DSM-III-R criteria for ADHD and 17 age-matched controls participated in the study. Brain electrical activity was recorded from 64 scalp sites. During the reference task, subjects pressed a microswitch on the unpredictable appearance of the letter X. During the CPT-AX, subjects were required to press the microswitch on the appearance of the letter X only if an A had preceded it.

RESULTS

In the interval between the appearances of the A and the X of the correct trials of the CPT-AX, control boys showed transient reductions in SSVEP latency at right prefrontal sites. By contrast, boys with ADHD showed no change or an increase in prefrontal SSVEP latency at right prefrontal sites.

CONCLUSION

Our results suggest increased speed of prefrontal neural processing in children without ADHD following a priming stimulus, and a deficit in such processes in children with ADHD.

Comparison between register and structured interview diagnoses of schizophrenia: a case for longitudinal diagnostic profiles

OBJECTIVE

Mental health registers contain diagnoses from serial contacts with mental health facilities over many years. This study examines the relationship between longitudinal diagnostic profiles and structured interview diagnoses. The aim is to improve the definition of diagnoses drawn from clinical case registers.

METHOD

The Tasmanian Mental Health Case Register includes 1922 individuals, each with at least one diagnosis of schizophrenia between 1965 and 1990. A representative subsample of 29 individuals were assessed by the structured diagnostic interview for DSM-III-R (SCID). Diagnostic agreement between Register and SCID diagnoses was compared.

RESULTS

Twenty-four subjects (82.8%) received a lifetime diagnosis of schizophrenia on the SCID. For each subject, 'schizophrenia diagnostic dominance', the percentage of register entries with schizophrenia diagnoses over total entries, was calculated. Agreement between register and SCID correlated positively with schizophrenia diagnostic dominance and negatively with register mood diagnoses.

CONCLUSIONS

Longitudinal diagnostic profiles on databases may be superior to cross-sectional clinical diagnoses in predicting structured interview diagnoses, and may be useful in defining caseness in epidemiological studies using register diagnoses.

Predictability of rehospitalisation over 5 years for schizophrenia, bipolar disorder and depression

OBJECTIVE

The aim of this study was to examine the rate of rehospitalisation for schizophrenia, bipolar disorder and depression over a 5-year period in Tasmania, and to identify predictors of the number and duration of readmissions.

METHOD

The Tasmanian Mental Health Register was used to study the 5-year pattern of rehospitalisation for all patients admitted to a Tasmanian public psychiatric inpatient facility with a primary diagnosis of schizophrenia, bipolar disorder or depression, in 1983 or 1984.

RESULTS

Seventy-one percent of patients receiving a diagnosis of schizophrenia were readmitted in the 5-year period, compared to 59% for bipolar disorder and 48% for depression. For all three diagnoses, the number of prior admissions was a predictor of the number of readmissions and the total number of days spent in hospital in the follow-up period. Age and sex also had significant effects, which varied across diagnostic groups.

CONCLUSIONS

A substantial proportion of patients hospitalised for schizophrenia, bipolar disorder or schizophrenia were rehospitalised during the next 5 years. Patients with more previous admissions had more readmissions than those with fewer previous admissions.

Epilepsies in twins: genetics of the major epilepsy syndromes

We studied twins to examine the genetics of epilepsy syndromes. We ascertained 358 twin pairs in whom one or both reported seizures. After evaluation, 253 of 358 (71%) had seizure disorders and 105 pairs were false positives. Among the monozygous (MZ) pairs, more were concordant for seizures (48 of 108; casewise concordance = 0.62 +/- 0.05) than among the dizygous (DZ) pairs (14 of 145; casewise concordance = 0.18 +/- 0.04). In 94% of concordant MZ pairs, and 71% of concordant DZ pairs, both twins had the same major epilepsy syndrome. When analyzed according to major epilepsy syndrome, the casewise concordances for generalized epilepsies (MZ = 0.82; DZ = 0.26), both idiopathic (MZ = 0.76; DZ = 0.33) and symptomatic (MZ = 0.83; DZ = 0), were greater than those for partial epilepsies (MZ = 0.36; DZ = 0.05), with intermediate values seen for febrile seizures (MZ = 0.58; DZ = 0.14) and unclassified epilepsies (MZ = 0.53; DZ = 0.18). We conclude that genetic factors are particularly important in the generalized epilepsies but also play a role in the partial epilepsies. The high frequency of concordant MZ pairs with the same major syndrome strongly suggests there are syndrome-specific genetic determinants rather than a broad genetic predisposition to seizures.

Attention-deficit hyperactivity disorder: a category or a continuum? Genetic analysis of a large-scale twin study

OBJECTIVE

To investigate heritability and continuum versus categorical approaches to attention-deficit hyperactivity disorder (ADHD), using a large-scale twin sample.

METHOD

A cohort of 1,938 families with twins and siblings aged 4 to 12 years, recruited from the Australian National Health and Medical Research Council Twin Registry, was assessed for ADHD using a DSM-III-R-based maternal rating scale. Probandwise concordance rates and correlations in monozygotic and dizygotic twins and siblings were calculated, and heritability was examined using the De Fries and Fulker regression technique.

RESULTS

There was a narrow (additive) heritability of 0.75 to 0.91 which was robust across familial relationships (twin, sibling, and twin-sibling) and across definitions of ADHD as part of a continuum or as a disorder with various symptom cutoffs. There was no evidence for nonadditive genetic variation or for shared family environmental effects.

CONCLUSIONS

These findings suggest that ADHD is best viewed as the extreme of a behavior that varies genetically throughout the entire population rather than as a disorder with discrete determinants. This has implications for the classification of ADHD and for the identification of genes for this behavior, as well as implications for diagnosis and treatment.

Seasonal affective disorder in Australia: is photoperiod critical?

OBJECTIVES

Seasonal affective disorder (SAD) is a variant of recurrent depression in which episodes are linked to a particular season, typically winter. SAD is understood as the extreme end of a continuum of seasonality in the general population. Photoperiod (the timing and duration of daylight) has been assumed to be aetiologically critical. The present research used a survey design to investigate the assumed centrality of photoperiod for SAD/seasonality in Australia. Two hypotheses were tested: that self-reported seasonality does not increase further from the equator and that seasonality does not stand alone from non-seasonal neurotic complaints.

METHOD

The sampling frame used was adult females on the Australian Twin Registry roll. A sample of 526 women residing across the latitudes of Australia responded to a survey based around the Seasonal Pattern Assessment Questionnaire (SPAQ). The SPAQ asks respondents to retrospectively report on season-related changes in mood and behaviour. The survey also contained three questionnaire measures of neurotic symptoms of anxiety and depression: the General Health Questionnaire (GHQ), the Community Epidemiological Survey for Depression (CES-D) and the State-Trait Anxiety Inventory-Trait (STAI-T).

RESULTS

Self-reported seasonality did not correlated with latitude (r = 0.01, NS). On the other hand, a substantial relationship was found between seasonality and each of the measures of non-seasonal complaints: GHQ (r = 0.35, p < 0.001); CES-D (r = 0.35, p < 0.001); and STAI-T (r = 0.30, p < 0.001).

CONCLUSIONS

Within the limitations of a design based on retrospective self-report, the findings of the present study suggest that the diathesis for SAD/seasonality may not be photoperiod-specific. At least in Australia, there is provisional support for the proposal that human seasonality may have a broader psychological component. The findings are discussed in terms of established research into normal mood, trait personality and non-seasonal depression.

Season of birth and schizophrenia in Tasmania

OBJECTIVE

The purpose of the present study was to determine whether there was a significant seasonal variation in the birth dates of patients with schizophrenia born in Tasmania.

METHOD

The season of birth in Tasmanian-born patients with schizophrenia (n = 1412), born between 1919-1970, was compared with general population data.

RESULTS

No significant variation in month or quarter of birth was detected for the subjects with schizophrenia. Neither was there any significant seasonal excess when data from different decades were analysed separately, nor for subsidiary analyses of gender or paranoid/non paranoid subtype.

CONCLUSION

These results are compared with those of six other published studies of Australasian-born subjects identified through registers in different States. While both positive and negative results are reported, no clear pattern emerges. The relevance of season of birth to the development of schizophrenia in Australia remains an open question.

Decline in diagnoses of schizophrenia in Tasmania during the period 1965-1990

Changes in the rates of diagnosis of schizophrenia in Tasmania, Australia during the period of 1965-1990 were examined using records from the State mental health case register. Analyses were restricted to subjects with diagnoses recorded between the ages of 20 and 29 years in order to reduce possible errors caused by age-standardized methods. There was a significant decrease in the rate of non-paranoid subtypes of schizophrenia in female subjects, accompanied by a commensurate rise in the rate of bipolar diagnoses in that group. Differential changes in male and female subjects support explanations of phenotypic shifts in presentation of psychosis as well as changes in diagnostic practice.

Characterization of the radical trapping activity of a novel series of cyclic nitrone spin traps

alpha-Phenyl-tert-butyl nitrone (PBN) is a nitrone spin trap, which has shown efficacy in animal models of oxidative stress, including stroke, aging, sepsis, and myocardial ischemia/reperfusion injury. We have prepared a series of novel cyclic variants of PBN and evaluated them for radical trapping activity in vitro. Specifically, their ability to inhibit iron-induced lipid peroxidation in liposomes was assessed, as well as superoxide anion (O2(-.)) and hydroxyl radical ((.)OH) trapping activity as determined biochemically and using electron spin resonance (ESR) spectroscopy. All cyclic nitrones tested were much more potent as inhibitors of lipid peroxidation than was PBN. The unsubstituted cyclic variant MDL 101,002 was approximately 8-fold more potent than PBN. An analysis of the analogs of MDL 101,002 revealed a direct correlation of activity with lipophilicity. However, lipophilicity does not solely account for the difference between MDL 101,002 and PBN, inasmuch as the calculated octanol/water partition coefficient for MDL 101,002 is 1.01 as compared to 1.23 for PBN. This indicated the cyclic nitrones are inherently more effective radical traps than PBN in a membrane system. The most active compound was a dichloro analog in the seven-membered ring series (MDL 104,342), which had an IC50 of 26 mum, which was 550-fold better than that of PBN. The cyclic nitrones were shown to trap (.)OH with MDL 101,002 being 20 25 times more active than PBN as assessed using 2-deoxyribose and p-nitrosodimethylaniline as substrates, respectively. Trapping of (.)OH by MDL 101,002 was also examined by using ESR spectroscopy. When Fenton's reagent was used, the (.)OH adduct of MDL 101,002 yielded a six-line spectrum with hyperfine coupling constants distinct from that of PBN. Importantly, the half-life of the adduct was nearly 5 min, while that of PBN is less than 1 min at physiologic pH. MDL 101,002 also trapped the O2(-.) radical to yield a six-line spectrum with coupling constants very distinct from that of the (.)OH adduct. In mice, the cyclic nitrones ameliorated the damaging effects of oxidative stress induced by ferrous iron injection into brain tissue. Similar protection was not afforded by the lipid peroxidation inhibitor U74006F, thus implicating radical trapping as a unique feature in the prevention of cell injury. Together, the in vivo activity, the stability of the nitroxide adducts, and the ability to distinguish between trapping of (.)OH and O2(-.) suggest the cyclic nitrones to be ideal reagents for the study of oxidative cell injury.

FRAXE and mental retardation

Mental impairment and instability of the CCG repeat at FRAXE is described in six kindreds. Cosegregation of FRAXA and FRAXE was found within one of these kindreds. Cytogenetic expression of FRAXE was shown to skip a generation when associated with a reduction in size of the CCG expansion when transmitted through a male; however, in general, transmission occurred through females and a copy number increased from one generation to the next. In these respects the behaviour of FRAXE paralleled that of FRAXA. A relationship between FRAXE and non-specific mental impairment is strongly suggested by the occurrence in these families of more mentally impaired male and female carriers, after removal of index cases, than could reasonably be expected by chance.

In vitro and in vivo activity of a novel series of radical trapping agents in model systems of CNS oxidative damage

Many laboratory and clinical studies suggest that oxygen radical formation and resultant cell damage contribute to CNS injury following stroke and neurotrauma. Accordingly, antioxidants represent a viable therapeutic approach for management of CNS oxidative damage. Recently, several investigators have reported that the spin trap PBN protects against stroked-induced damage and reduces aging-associated neurological deficits. We have prepared and tested a cyclic analog of PBN, MDL 101,002, in a number of in vitro and in vivo assays designed to assess its neuroprotective properties. MDL 101,002 was found to be an effective .OH trap, to inhibit lipid peroxidation, and to decrease infarct size in a gerbil model of stroke. These results further indicate that oxidative damage arising from stroke contributes to infarct formation, and that spin traps are effective in ameliorating ischemia and reperfusion-induced CNS injury.

Transmitting males and carrier females in fragile X--revisited

Fragile X "transmitting males" have customarily been defined as phenotypically normal hemizygotes, who show very few or no fragile sites, and who transmit the fragile X premutation to phenotypically normal daughters. However, an objective justification of this definition was lacking. The discovery of an unstable CCG repeat as the genetic basis of fragile X further emphasized the apparent distinction between the "normal transmitting males" with short repeat and expression of the FMR1 gene, and the affected males with larger repeats (delta > 0.6 kb) and a complete lack of FMR1 transcription. We have recently shown that the transition between these two groups in phenotypic expression of fragile X is gradual, mainly on account of methylation mosaicism. However, there were insufficient data on the phenotype within the short repeat (0.0 < delta < 0.6) range. In this paper we approach this problem by comparing some clinical, anthropometric, and psychometric data from a sample of normal transmitting males with those from their non-fragile X male relatives. Moreover, female carriers with short repeat are compared for the same traits with their non-fragile X female relatives. The results have shown that both males and females with a short repeat differed significantly from normal on several psychometric and physical measurements, and males only showed differences in typical facial traits. Further studies of genotype-phenotype correlations within the short repeat range, including the estimate of FMR1 gene function and a more exact estimate of repeat size, is required before genetic explanation for the clinical findings can be provided.(ABSTRACT TRUNCATED AT 250 WORDS)

Does IQ decline with age in fragile-X? A methodological critique

The recent claims for a decline in intelligence test performance in males and females with fragile-X (fra(X)) syndrome have implications both clinically and in evaluating the underlying neurological basis. This commentary identifies three key issues in evaluating evidence for a decline and in planning future, more co-ordinated efforts. These are (1) problems in combining data across different intelligence tests and/or different ages with potentially incompatible norms, task demands, and models of the structure of intelligence; (2) limitations in applying to low ability persons tests designed to discriminate best around the population average; and (3) specific cognitive deficits and behavioral problems in fra(X) individuals which may be confounded with the task demands of particular IQ tests at particular ages. While the decline in ability may be a real phenomenon rather than an artifact, recommendations are made about the psychometric requirements for a larger and more definitive collaborative study.

Twin birth is not a risk factor for seizures

There is a belief that perinatal factors are a major cause of epilepsy. We studied a community-based sample of twins, a group with a marked excess of adverse perinatal events. The observed number of non-twin siblings with seizures did not differ from that predicted by the age-specific cumulative incidence rate of seizures (4.2% at age 10 years) in the twins. The types of epilepsies in the twins were largely benign and self-limited and not those associated with brain damage. Zygosity, birth order, and birth weight did not predict affected status. Within affected sibships, the frequency of seizures in co-twins of dizygotic probands (9%) was not different from the frequency in non-twin siblings (12%) but was much less than the frequency in co-twins of monozygotic probands (38%; p < 0.001), reflecting a major genetic component to certain epilepsies. These data show that twins do not have an increased risk of seizures and strongly suggest that perinatal factors have little bearing on the etiology of the common epilepsies in the community.

Genotype-phenotype relationships in fragile X syndrome: a family study

Relationships between the measures of intellectual and physical status in the fragile X syndrome and the size of amplification of the fragile X-specific fragment, equivalent to the number of CCG repeats within the FMR1 locus, were studied by a maximum-likelihood scoring technique for analysis of pedigree data. This allows for estimation of random effects (genetic and environmental variance) concurrently with other (fixed) effects in a quantitative trait. FMR1 expression is usually shut down in males penetrant for the fragile X syndrome who have hypermethylated CCG amplifications of > or = 0.6 kb. The assumption of the step versus curvilinear function representing this relationship was tested by the likelihood-ratio criterion. The maximum-likelihood parameters were based on the most appropriate model for each measure. The results were indicative of the presence of a curvilinear relationship between the amplification size and the two intellectual scores, the Peabody Picture Vocabulary Test and Block Design Test, measuring verbal and spatial abilities, respectively. Reasons for the unexpected curvilinear regression between the amplification size and intellectual scores were explained further by methylation analysis of fragile X males with amplifications of 0.6 < delta < or = 1.2 kb who appeared to be responsible for the curvilinearity of the relationship. Four of these showed unmethylated status of the amplified bands in lymphocytes, which were presumably transcriptionally active. Removal of the aberrant individuals led to the anticipated step function between amplification and intellectual scores. For the combined anthropometric score, as well as for several single physical measures, the step function was the most appropriate model regardless of the inclusion or omission of the aberrant individuals in the pedigree sample.

Phenotypic and genetic affinities among ethnic populations in Daghestan (Caucasus, Russia): a comparison of polymorphic, physical, neurophysiological and psychological traits

Daghestan contains many distinct populations characterized by different degrees of isolation, ethnic backgrounds and ecological conditions. This report introduces a large-scale family study conducted in seven Daghestan populations as well as in Moscow, using four categories of measures: (1) single gene polymorphisms, (2) anthropometric, (3) physiological, and (4) psychological quantitative traits. Such a study permits the analysis of both phenotypic and genetic variation within and between populations. The implications of such variation are discussed, especially in the context of the measures used. These derive from Soviet conceptualizations of the nervous system and related assessment of individual differences, and vary considerably from conventional Western approaches to behaviour. From the anthropometric through the physiological to the behavioural measures there was a clear trend towards increased phenotypic variation but reduced genetic variation. Possibly because the genetic variance was less on the more complex phenotypes, measures of generalized distance indicated much greater population similarity when based on phenotypic data on the genetic component of variation. Issues that arise when using behavioural traits to study human population diversity are discussed, particularly in relation to inbreeding and the specific cultural and linguistic practices in the Daghestan region.

Between-generation differences in ascertainment and penetrance: relevance to genetic hypotheses in fragile X

Between-generation differences in ascertainment were examined in 54 extended fragile X pedigrees, where all available members were clinically, psychometrically, and cytogenetically investigated. In 24 families a diagnosis was verified by molecular characterization using the pfxa3 fragile X-specific probe. We found considerable differences between generations in relative proportions of affected fragile X subjects versus 'non-penetrant' carriers. We also found deviation in the segregation ratio in unbiased samples of relatives in pedigrees. We claim that these irregularities are influenced by different rates of ascertainment, depending on the clinical expression of the condition (penetrance) and the fertility of fragile X individuals in a pedigree, as well as by the thoroughness of clinical investigation in individual families. Penetrance and fertility were estimated in fragile X females assessed by psychometric tests, and they were compared with earlier estimates based on a subjective judgement of their intellectual status. We suggest that the standard correction for ascertainment bias, such as has been applied in segregation analysis of this condition, is not sufficient to adjust for all types of bias.

Fragile X family with unusual digital and facial abnormalities, cleft lip and palate, and epilepsy

We present a fragile X family with unusual clinical manifestations. These findings, which often occur in the X-linked FG syndrome, include minor limb anomalies, cleft lip and palate, characteristic facial appearance, gastrointestinal problems and epilepsy, and intellectual disability. In a total sample of 54 fra(X) families, the frequency of minor limb anomalies was estimated to be 32% in the affected males and 19% in the female heterozygotes. These anomalies tend to occur in several members of the same family, where some craniofacial abnormalities reported as characteristic of the FG syndrome have also been encountered. Possible mechanisms for the occurrence of these unusual manifestations in the fra(X) families are discussed.

Selective breeding for increased cholinergic function: biometrical genetic analysis of muscarinic responses

Biometric genetic analyses of behavioral and physiologic responses known to be related to muscarinic cholinergic receptors (hypothermia, hypoactivity, inhibited avoidance, and reduced responding for water) were studied in genetic crosses and backcrosses of the Flinders sensitive line (FSL) and Flinders resistant line (FRL) of rats. The FSL rats were more sensitive to the direct muscarinic agonists, arecoline and oxotremorine, and to the indirect agonist, physostigmine, than any other group. The next most sensitive group was the F1 x FSL backcross, followed by the F2, F1, F1 x FRL backcross, and the FRL, in that order. These differences between the genetic groups could be accounted for completely by either solely additive or additive plus dominance genetic factors. When dominance genetic factors contributed to the differences among groups (6 out of 15), the F1 responded like the FRL rats. The variance of the responses measured made it impossible to obtain reliable estimates of the number of genes involved in many instances; when such estimates were possible, several genes (greater than or equal to 3) appeared to be involved. We conclude that muscarinic sensitivity in rats is under genetic control, with the greatest contribution coming from additive genetic factors. Because the FSL rat appears to be a genetic animal model of depression, the finding of several genes influencing muscarinic responses may help account for the difficulties investigators have had in locating a single major gene or biological marker for human depressive disorders.

Problems in ascertainment of transmitting males in Martin-Bell syndrome

The difficulty of assigning families affected with the Martin-Bell syndrome (MBS) into the category of male transmission is emphasised and illustrated by examples of 3 MBS families. These examples demonstrate how the ability to detect transmitting males depends on the number of generations available for investigation, and also on the "spread" of clinical investigation across many branches of the family regardless of what appears to be an unremarkable family history. Some unusual properties of male transmission are shown, and the problem of selective ascertainment of the particular MBS male individuals in different generations in a set of pedigrees is discussed.

What information should the multiple birth family receive before, during and after the birth?

Advances in the management of the multiple pregnancy and delivery must be accompanied by corresponding improvements in service access outside key centres and especially in the information families receive about what may happen during or after the pregnancy. A major review of birthing services in Victoria has focussed attention on four areas where the quality of information is often inadequate. 1) Prepregnancy and the standard of counselling about the incidence of multiples as a result of fertility drugs and in vitro fertilization procedures and about problems which may accompany a multiple birth. 2) Antenatal: At what stage of the pregnancy should parents be told of the multiple pregnancy and how should monitoring of the mother and procedures such as bedrest take into account what are often conflicting demands within the family? 3) Perinatal: Families are frequently illprepared for a cesarean delivery and for the procedures for premature multiples. The problem is often compounded by separation of the mother from one or both twins. While bereavement services are improving, much still needs to be learned about handling congenital abnormalities in one or more multiples. 4) Postnatal: Irrespective of the level of prenatal advice, families greatly underestimate the workload with multiples. The resulting stress contributes to the incidence of postnatal depression, child abuse and divorce now being reported from multiple birth families. Some suggestions are made from social psychology and genetic counselling about how families can best handle risk information to achieve the goal of neither under- nor overestimating the risks at these different stages of the multiple pregnancy.

"Twins in school". An Australia-wide program

The multiple birth family is more likely to have a dispute with the education system than with any other service. So many potential areas of conflict exist over the abilities and behaviour of multiples and over such issues as separation or keeping back one twin. One reason for disputes is the lack of good data to adequately reflect the different perspectives of parents and teachers and the differing needs of families: the same solution does not apply to all. To provide the first large-scale data base and building upon an initial survey of 85% of all primary school teachers in South Australia, the LaTrobe Twin Study and AMBA worked with Education Departments to set-up in each state Education Research Teams (ERTs) of parents of multiples who were also teachers. The ERTs were crucial in three phases. 1) Developing and circulating questionnaires and publicising the nationwide survey. 784 families and 1264 teachers of their children completed these questionnaires, many reporting that simply having to address the issues raised in the questionnaire was a valuable learning experience. 2) Exploring the data base. Issues arising included the very different bases on which parents and teachers judged separation desirable, with teachers emphasising the unsubstantiated claim that separation is essential to individual development. Separation became more common over the first three years of schooling but 20-25% of twins separated one year were back together the next. 3) Running regional meetings of parents, teachers and administrators to discuss the results and to pool experiences and plan policies at the local level. A need clearly exists to improve the level of consultation between families and school personnel and to ensure the widespread availability of information which identifies key issues in making decisions for that multiple birth family.

Twin children in volunteer registries: biases in parental participation and reporting

The biases in voluntary participation by adult twins are well known but less attention has been paid to twin children where parents decide on participation and provide much of the information. Several aspects of reporting including the assessment of zygosity are compared in four large Australian data bases: 1) a nationwide compulsory (and hence representative) survey of literacy and numeracy; 2) a nationwide "Twins in School" survey of parents and teachers of twins run through Education Departments and AMBA, the parents organisation in conjunction with LaTrobe; 3) the LaTrobe Twin Study which is a longitudinal program involving frequent interactions between families and researchers, and 4) the Australian NHMRC Twin Registry which has surveyed a large sample of their families with twin children by mail. One potential bias comes when recruitment is on a continuing basis as in the LaTrobe Twin Study and the Australian Twin Registry when differences between "early" and "late" enrolling families arise. One difference between the four samples arose from parents being much more likely to contrast their twins and to report problems in one but not the other, whereas teachers' and psychologists' assessments of these same children generally reported much smaller intrapair differences. Future studies should have some common questions to provide comparative data on such biases. Key questions are proposed for this area, mainly on the perceived need for different forms of remediation, together with other recommendations about the minimal essential baseline data set for a registry.

Neuropsychological dimensions of the fragile X syndrome: support for a non-dominant hemisphere dysfunction hypothesis

This study contends that males with the fragile X syndrome feature problems in the visuospatial sphere as compared with Down syndrome males matched on vocabulary ability. Fragile X males suffer impairments of constructional functions, as demonstrated by their poor performance on block construction tests and on drawing tasks. These problems exist in association with visuoperceptive impairments, including the inability to reliably estimate angular relationships (Judgement of Line Orientation). They have shortened Digit and Corsi spans, and may feature some deficits in left hand co-ordination. The observation of a pervasive non-verbal deficit may also apply to carrier females, who despite functioning at an overall higher level, feature a similar pattern of deficits. It is possible that the deficit in non-dominant hemisphere functioning may be a pathognomonic feature of the chromosomal abnormality.

The relevance of the health belief model to Australian smokers

The Health Belief Model is one of the few models predicting health behavior which explicitly evaluates the role of cues to action from the doctor or others. Rarely have such cues to action been examined formally by the comparison of groups receiving different interventions. Initial and follow-up data covering a wide range of sociopsychological variables were gathered from typical smokers among family-practice patients participating in an Australian quit-smoking program. Patients were randomly assigned either to a control or experimental group, the latter receiving the Give-Up Smoking (GUS) kit, and quit-smoking advice from their doctor. Factor analysis of the initial data largely confirmed the clusters of the Health Belief Model. At follow-up, after the experimental and control group treatment, a totally different factor structure emerged, comprising some very specific sociopsychological variables and cues to action. Implications are discussed for the Health Belief Model relative to other health behavior models.

Clinical features and reproductive patterns in fragile X female heterozygotes

Clinical findings are presented on 113 fragile X female heterozygotes from 44 families, based on physical examination, behavioural assessment, and reproductive history. In 85% of a subsample of 92 adult females non-verbal IQ score derived from the Block Design test was 85 or less. Verbal ability deficits were much less common. Typical facial characteristics, irregular teeth, and hypermobility of finger joints occurred in approximately 40% of adult females, but facial abnormalities were less common in children. Some physical anomalies and the level of intellectual impairment were, in adult carriers, associated with the presence of fragile X sites. The commoner physical anomalies or typical facial characteristics and intellectual abilities differed significantly between the known female heterozygotes and their 40 presumed normal relatives. Frequency of miscarriages was increased in fragile X females; in spite of this, a moderate increase in the number of children has been encountered in female carriers with borderline intellectual impairment. This important problem has genetical implications and needs further investigation. The importance is emphasised of a more detailed clinical examination of the females at risk in fragile X families.

Individual variation and specific cognitive deficits in the fra(X) syndrome

Mental retardation has been associated with fra(X) but comprehensive psychological evaluation has rarely been applied to 2 major behavioral questions 1) the extent of individual variation in IQ among fra(X) males and the possibility of some fra(X) males being of normal IQ; and 2) whether there is a depression in general IQ or whether specific abilities are impaired. The problems of developing an effective battery of tests for assessing fra(X) are discussed. These questions were examined in 54 individuals, comprising fra(X) males, their obligate carrier mothers and those sisters shown to have the fra(X). Among noninstitutionalised males nonverbal IQ as measured on a Block Design test ranged from 100 to 0, and vocabulary scores while generally higher, ranged from 79-33. The males scored low on a digit span memory task, while performance on a memory of objects task was adequate. Despite lower overall scores, a similar pattern and variability emerged in institutionalised males. Daughters were extremely variable in performance and the mothers performed much better, supporting the view that women who have children are a selected subset of fra(X) syndrome individuals. The performance of one male is discussed in detail. His vocabulary and nonverbal IQ scores were normal, despite his having other specific cognitive deficits. The pattern of abilities and behavior seen in fra(X) may result in an overestimation of intelligence and underestimation of penetrance when based on clinical impressions rather than formal psychological assessment. The implications of this for molecular and for population genetic approaches to fra(X) are discussed.