Unclassified white matter disorders: A diagnostic journey requiring close collaboration between clinical and laboratory services

BACKGROUND

Next generation sequencing studies have revealed an ever-increasing number of causes for genetic disorders of central nervous system white matter. A substantial number of disorders are identifiable from their specific pattern of biochemical and/or imaging findings for which single gene testing may be indicated. Beyond this group, the causes of genetic white matter disorders are unclear and a broader approach to genomic testing is recommended.

AIM

This study aimed to identify the genetic causes for a group of individuals with unclassified white matter disorders with suspected genetic aetiology and highlight the investigations required when the initial testing is non-diagnostic.

METHODS

Twenty-six individuals from 22 families with unclassified white matter disorders underwent deep phenotyping and genome sequencing performed on trio, or larger, family groups. Functional studies and transcriptomics were used to resolve variants of uncertain significance with potential clinical relevance.

RESULTS

Causative or candidate variants were identified in 15/22 (68.2%) families. Six of the 15 implicated genes had been previously associated with white matter disease (COL4A1, NDUFV1, SLC17A5, TUBB4A, BOLA3, DARS2). Patients with variants in the latter two presented with an atypical phenotype. The other nine genes had not been specifically associated with white matter disease at the time of diagnosis and included genes associated with monogenic syndromes, developmental disorders, and developmental and epileptic encephalopathies (STAG2, LSS, FIG4, GLS, PMPCA, SPTBN1, AGO2, SCN2A, SCN8A). Consequently, only 46% of the diagnoses would have been made via a current leukodystrophy gene panel test.

DISCUSSION

These results confirm the importance of broad genomic testing for patients with white matter disorders. The high diagnostic yield reflects the integration of deep phenotyping, whole genome sequencing, trio analysis, functional studies, and transcriptomic analyses.

CONCLUSIONS

Genetic white matter disorders are genetically and phenotypically heterogeneous. Deep phenotyping together with a range of genomic technologies underpin the identification of causes of unclassified white matter disease. A molecular diagnosis is essential for prognostication, appropriate management, and accurate reproductive counseling.

Germ cell arrest associated with aSETX mutation in ataxia oculomotor apraxia type 2

Ataxia with oculomotor apraxia type 2 (AOA2) is a rare autosomal recessive neurodegenerative disorder characterized by cerebellar atrophy, peripheral neuropathy and oculomotor apraxia. It is caused by mutations in the SETX gene that encodes senataxin, a ubiquitously expressed protein that mediates processes, including transcription, transcription termination, DNA repair, RNA processing, DNA-RNA hybrid (R-loop) elimination and telomere stability. In mice, senataxin is essential for male germ cell development and fertility through its role in meiotic recombination and sex chromosome inactivation. AOA2 is associated with hypogonadism in women, but there are no reports of hypogonadism or infertility in men. We describe the first case of human male infertility caused by germ cell arrest in a man with AOA2. Our patient has a homozygous mutation in the SETX gene (NC_000009.11:g.135158775dup), which results in a frameshift and premature protein termination (NM_015046.6:c.6422dup, p.[Ser2142Glufs*23]). In accordance with the murine phenotype, testis histology revealed disrupted seminiferous tubules with spermatogonia and primary spermatocytes, but absent spermatids. Collectively, these data support an essential role of senataxin in human spermatogenesis, and provide a compelling case that men with AOA2 should be counselled at diagnosis about the possibility of infertility.

Variants in ACTG2 underlie a substantial number of Australasian patients with primary chronic intestinal pseudo-obstruction

BACKGROUND

Primary chronic intestinal pseudo-obstruction (CIPO) is a rare, potentially life-threatening disorder characterized by severely impaired gastrointestinal motility. The objective of this study was to examine the contribution of ACTG2, LMOD1, MYH11, and MYLK mutations in an Australasian cohort of patients with a diagnosis of primary CIPO associated with visceral myopathy.

METHODS

Pediatric and adult patients with primary CIPO and suspected visceral myopathy were recruited from across Australia and New Zealand. Sanger sequencing of the genes encoding enteric gamma-actin (ACTG2) and smooth muscle leiomodin (LMOD1) was performed on DNA from patients, and their relatives, where available. MYH11 and MYLK were screened by next-generation sequencing.

KEY RESULTS

We identified heterozygous missense variants in ACTG2 in 7 of 17 families (~41%) diagnosed with CIPO and its associated conditions. We also identified a previously unpublished missense mutation (c.443C>T, p.Arg148Leu) in one family. One case presented with megacystis-microcolon-intestinal hypoperistalsis syndrome in utero with subsequent termination of pregnancy at 28 weeks' gestation. All of the substitutions identified occurred at arginine residues. No likely pathogenic variants in LMOD1, MYH11, or MYLK were identified within our cohort.

CONCLUSIONS AND INFERENCES

ACTG2 mutations represent a significant underlying cause of primary CIPO with visceral myopathy and associated phenotypes in Australasian patients. Thus, ACTG2 sequencing should be considered in cases presenting with hypoperistalsis phenotypes with suspected visceral myopathy. It is likely that variants in other genes encoding enteric smooth muscle contractile proteins will contribute further to the genetic heterogeneity of hypoperistalsis phenotypes.

A longitudinal study of the SF-36 version 2 in Friedreich ataxia

OBJECTIVES

The Medical Outcomes Study 36 item Short-Form Health Survey (SF-36) is one of the most commonly used patient reported outcome measure. This study aimed to examine the relationship between SF-36 version 2 (SF-36V2) summary scores and Friedreich ataxia (FRDA) clinical characteristics, and to investigate the responsiveness of the scale, in comparison with the Friedreich Ataxia Rating Scale (FARS), over 1, 2 and 3 years.

MATERIALS AND METHODS

Descriptive statistics were used to examine the characteristics of the cohort at baseline and years 1, 2 and 3. Correlations between FRDA clinical characteristics and SF-36V2 summary scores were reported. Responsiveness was measured using paired t tests.

RESULTS

We found significant correlations between the physical component summary (PCS) of the SF-36V2 and various FRDA clinical parameters but none for the mental component summary. No significant changes in the SF-36V2 were seen over 1 or 2 years; however, PCS scores at Year 3 were significantly lower than at baseline (-3.3, SD [7.6], P=.01). FARS scores were found to be significantly greater at Years 1, 2 and 3 when compared to baseline.

CONCLUSIONS

Our findings suggest that despite physical decline, individuals with FRDA have relatively stable mental well-being. This study demonstrates that the SF-36V2 is unlikely to be a useful tool for identifying clinical change in FRDA therapeutic trials.

A Novel Mechanism for Human Cardiac Ankyrin-B Syndrome due to Reciprocal Chromosomal Translocation

BACKGROUND

Cardiac rhythm abnormalities are a leading cause of morbidity and mortality in developed countries. Loss-of-function variants in the ANK2 gene can cause a variety of cardiac rhythm abnormalities including sinus node dysfunction, atrial fibrillation and ventricular arrhythmias (called the "ankyrin-B syndrome"). ANK2 encodes ankyrin-B, a molecule critical for the membrane targeting of key cardiac ion channels, transporters, and signalling proteins.

METHODS AND RESULTS

Here, we describe a family with a reciprocal chromosomal translocation between chromosomes 4q25 and 9q26 that transects the ANK2 gene on chromosome 4 resulting in loss-of-function of ankyrin-B. Select family members with ankyrin-B haploinsufficiency due to the translocation displayed clinical features of ankyrin-B syndrome. Furthermore, evaluation of primary lymphoblasts from a carrier of the translocation showed altered levels of ankyrin-B as well as a reduced expression of downstream ankyrin-binding partners.

CONCLUSIONS

Thus, our data conclude that, similar to previously described ANK2 loss-of-function "point mutations", large chromosomal translocations resulting in ANK2 haploinsufficiency are sufficient to cause the human cardiac ankyrin-B syndrome. The unexpected ascertainment of ANK2 dysfunction via the discovery of a chromosomal translocation in this family, the determination of the familial phenotype, as well as the complexities in formulating screening and treatment strategies are discussed.

To tell or not to tell - what to do about p.C282Y heterozygotes identified by HFE screening

Hereditary hemochromatosis (HH) is a common preventable disorder of iron overload that can result in liver cirrhosis and reduced lifespan. Most HH is due to homozygosity for the HFE p.C282Y substitution. We conducted a study of screening for p.C282Y in high schools where p.C282Y heterozygotes (CY) individuals were informed of their genotype by letter. We studied whether these individuals understood the implications of their genotype, whether this resulted in anxiety or reduced health perception and whether cascade testing was higher in families of CY than wild-type homozygous (CC) individuals. We found 586 of 5757 (1 in 10) screened individuals were CY. One month after receiving their result, 83% correctly answered that they have one copy of p.C282Y. There was no adverse change in anxiety or health perception from prior to screening to 1 month after receiving results. Significantly more family members of CY individuals than CC individuals were informed about HH and had testing for HH. In conclusion, we found that informing CY individuals of their genotype does not increase anxiety and the implications are generally well understood. This leads to cascade testing in a minority of families. CY individuals should be informed of their genetic status when identified by population screening.

A functional MRI study of motor dysfunction in Friedreich's ataxia

Friedreich's ataxia (FRDA) is the most common form of hereditary ataxia. In addition to proximal spinal cord and brain stem atrophy, mild to moderate atrophy of the cerebellum has been reported in advanced FRDA. The aim of this study was to examine dysfunction in motor-related areas involved in the execution of finger tapping tasks in individuals with FRDA, and to investigate functional re-organization of cortico-cerebellar, cortico-striatal and parieto-frontal loops as a result of the cerebellar pathology. Thirteen right-handed individuals with FRDA and fourteen right-handed controls participated. Functional MRI images were acquired during four different finger tapping tasks consisting of visually cued regular and irregular single finger tapping tasks, a self-paced regular finger tapping task, and a visually cued multi-finger tapping task. Both groups showed significant activation of the motor-related network including the pre-central cortex and supplementary motor area bilaterally; the left primary motor cortex, somatosensory cortex and putamen; and the right cerebellum. During the visually cued regular finger tapping task, the right hemisphere of the cerebellar cortex, bilateral supplementary motor areas and right inferior parietal cortex showed higher activation in the healthy control group, while in individuals with FRDA the left premotor cortex, left somatosensory cortex and left inferior parietal cortex were more active. In addition, during the visually cued irregular finger tapping task, the right middle temporal gyrus in the control group and the right superior parietal lobule and left superior and middle temporal gyri in the individuals with FRDA showed higher activation. During visually cued multi-finger tapping task, the control group showed higher activation in the bilateral middle frontal gyri, bilateral somatosensory cortices, bilateral inferior parietal lobules, left premotor cortex, left supplementary area, right superior frontal gyrus and right cerebellum, while individuals with FRDA showed increased activity in the left inferior parietal lobule, left primary motor cortex, left middle occipital gyrus, right somatosensory cortex and the left cerebellum. Only the right crus I/II of the cerebellum showed higher activation in individuals with FRDA during the self-paced regular finger tapping task, whereas wide-spread regions including the left superior frontal gyrus, left central opercular cortex, left somatosensory cortex, left putamen, right cerebellum, bilateral primary motor cortices, bilateral inferior parietal lobules and the left insula were more active in the control group. Although the pattern of the BOLD signal from the putamen was different during the self-paced regular finger tapping task to the other tasks in controls, in individuals with FRDA there was no distinction of the signal between the tasks suggesting that primary cerebellar pathology may cause secondary basal ganglia dysregulation. While individuals with FRDA tapped at a slightly lower rate (0.59Hz) compared with controls (0.74Hz) they showed significantly decreased activity of the SMA and the inferior parietal lobule, which may suggest disruption to the fronto-parietal connections. These findings suggest that the motor impairments in individuals with FRDA result from dysfunction extending beyond the spinal cord and cerebellum to include sub-cortical and cortical brain regions.

Decreased functional brain activation in Friedreich ataxia using the Simon effect task

The present study applied the Simon effect task to examine the pattern of functional brain reorganization in individuals with Friedreich ataxia (FRDA), using functional magnetic resonance imaging (fMRI). Thirteen individuals with FRDA and 14 age and sex matched controls participated, and were required to respond to either congruent or incongruent arrow stimuli, presented either to the left or right of a screen, via laterally-located button press responses. Although the Simon effect (incongruent minus congruent stimuli) showed common regions of activation in both groups, including the superior and middle prefrontal cortices, insulae, superior and inferior parietal lobules (LPs, LPi), occipital cortex and cerebellum, there was reduced functional activation across a range of brain regions (cortical, subcortical and cerebellar) in individuals with FRDA. The greater Simon effect behaviourally in individuals with FRDA, compared with controls, together with concomitant reductions in functional brain activation and reduced functional connectivity between cortical and sub-cortical regions, implies a likely disruption of cortico-cerebellar loops and ineffective engagement of cognitive/attention regions required for response suppression.

The Fitts task reveals impairments in planning and online control of movement in Friedreich ataxia: reduced cerebellar-cortico connectivity?

Friedreich ataxia (FRDA) is the most common of the inherited ataxias. We have suggested that people with FRDA may have impairment in cognitive and/or psychomotor capacity either due to disturbance of projections of the cerebellum to the cortex, direct cortical pathology or perhaps both. To further explore this possibility, we used a movement task incorporating Fitts' Law, a robust description of the relationship between movement time and accuracy in goal-directed aiming movements. By manipulating task difficulty, according to target size and distance, we were able to quantify processes related to motor planning in 10 individuals with FRDA and 10 matched control participants. Compared to control participants, people with FRDA were significantly disadvantaged in terms of movement time to targets with an increasing index of difficulty. Successful completion of this task requires both preplanning of movement and online error detection and correction. The cerebellum and its connections to the frontal cortex via cerebro-ponto-cerebello-thalamo-cerebral loops are fundamental to both processes. These results lend further support to our contention that in FRDA these loops are impaired, reflecting a failure to access prefrontal/anterior regions necessary for effective management of preplanning of movement and online error correction.

Impaired inhibition of prepotent motor tendencies in Friedreich ataxia demonstrated by the Simon interference task

Friedreich ataxia (FRDA) is the most common of the genetically inherited ataxias. We recently demonstrated that people with FRDA have impairment in motor planning - most likely because of pathology affecting the cerebral cortex and/or cerebello-cortical projections. We used the Simon interference task to examine how effective 13 individuals with FRDA were at inhibiting inappropriate automatic responses associated with stimulus-response incompatibility in comparison with control participants. Participants had to respond to arrow targets according to two features which were either congruent or incongruent. We found that individuals with FRDA were differentially affected in reaction time to incongruent, compared with congruent stimuli, when compared with control participants. There was a significant negative correlation between age of onset and the incongruency effect, suggesting an impact of FRDA on the developmental unfolding of motor cognition, independent of the effect of disease duration. Future neuroimaging studies will be required to establish whether this dysfunction is due to cerebellar impairment disrupting cerebro-ponto-cerebello-thalamo-cerebral loops (and thus cortical function), direct primary cortical pathology, or a possible combination of the two.

Evaluation of a multi-disease carrier screening programme in Ashkenazi Jewish high schools

A screening programme for Tay Sachs disease (TSD) carrier status was introduced in high schools in Victoria, Australia in 1997, and was expanded to screen for six other genetic conditions common in the Ashkenazi Jewish population in 2008. The aim of this study was to evaluate the current programme and compare it with an evaluation of the programme when screening was offered for TSD alone. All students from Jewish high schools in Melbourne who offered the programme in 2009 were invited to participate in the study. A purpose-designed questionnaire explored the following domains: knowledge (disease and genetics), reasons for screening, anxiety, and predicted negative feelings if found to be a carrier. Two hundred and seventy-three students were offered screening, and 272 (99.6%) completed the questionnaire. Only two students chose not to have screening. Two hundred and seventy-one students were in the penultimate year of high school (99.6%) and 222 were of Ashkenazi Jewish descent (82.5%). The main reasons for choosing screening were the desire to know carrier status and convenience. Knowledge level decreased and negative feelings increased in the current cohort compared to that when screening was offered for TSD alone. We conclude that the current programme is efficient, although increasing the number of conditions resulted in a decrease in knowledge and increase in predicted negative feelings if found to be a carrier of one of the conditions. This has implications for multi-disease screening programmes that will increase in frequency as more conditions can be screened for and costs diminish.

Genetic selection for deafness: the views of hearing children of deaf adults

The concept of selecting for a disability, and deafness in particular, has triggered a controversial and sometimes acrimonious debate between key stakeholders. Previous studies have concentrated on the views of the deaf and hard of hearing, health professionals and ethicists towards reproductive selection for deafness. This study, however, is the first of its kind examining the views of hearing children of deaf adults towards preimplantation genetic diagnosis and prenatal diagnosis to select for or against deafness. Hearing children of deaf adults (or CODAs, as they call themselves, and are widely known in the deaf community) straddle both the deaf and hearing worlds, and this dual perspective makes them ideally placed to add to the academic discourse concerning the use of genetic selection for or against deafness. The study incorporated two complementary stages, using initial, semistructured interviews with key informants (CODAs and health professionals) as a means to guide the subsequent development of an electronic survey, completed anonymously by 66 individuals. The participants shared many of the same views as deaf individuals in the D/deaf (or "culturally deaf") community. The similarities extended to their opinions regarding deafness not being a disability (45.5% believed deafness was a distinct culture rather than a disability), their ambivalence towards having hearing or deaf children (72.3% indicated no preference) and their general disapproval of the use of genetic technologies to select either for or against deafness (60% believed that reproductive technologies, when used to select for or against deafness, should not be available to the community).

SMARCB1/INI1 maternal germ line mosaicism in schwannomatosis

Schwannomatosis is characterized by the development of multiple schwannomas of the nervous system, but without the occurrence of vestibular schwannomas. Most cases of schwannomatosis are thought to be sporadic, representing the first case in a family due to a new mutation in the causative gene. We recently identified SMARCB1/INI1 as a schwannomatosis-predisposing gene. Here, we analyzed this gene in a schwannomatosis family with two affected children, but with clinically unaffected parents. Both affected individuals carried a constitutional SMARCB1 mutation, c.1118+ 1G>A, that changes the donor splice site sequence of intron 8, causing skipping of exon 8 and resulting in the in-frame deletion of 132 nucleotides in the transcript. The mutation was not evident in constitutional DNA of the parents. Haplotyping revealed that the chromosome 22 segment that carries the mutant SMARCB1 allele originated from the mother. She transferred the same chromosome 22 segment, however, with a wild-type SMARCB1 copy, to a third unaffected child. Our findings indicate that the mother is germ line mosaic for the SMARCB1 mutation. In conclusion, our study shows for the first time that germ line mosaicism may occur in schwannomatosis, which has implications for genetic counseling in this disease.

Mutant torsinA interacts with tyrosine hydroxylase in cultured cells

A specific mutation (DeltaE302/303) in the torsinA gene underlies most cases of dominantly inherited early-onset torsion dystonia. This mutation causes the protein to aggregate and form intracellular inclusion bodies in cultured cells and animal models. Co-expression of the wildtype and mutant proteins resulted in the redistribution of the wildtype protein from the endoplasmic reticulum to inclusion bodies in cultured HEK293 cells, and this was associated with increased interaction between the two proteins. Expression of DeltaE302/303 but not wildtype torsinA in primary postnatal midbrain neurons resulted in the formation of intracellular inclusion bodies, predominantly in dopaminergic neurons. Tyrosine hydroxylase was sequestered in these inclusions and this process was mediated by increased protein-protein interaction between mutant torsinA and tyrosine hydroxylase. Analysis in an inducible neuroblastoma cell culture model demonstrated altered tyrosine hydroxylase activity in the presence of the mutant but not wildtype torsinA protein. Our results suggest that the interaction of tyrosine hydroxylase and mutant torsinA may contribute to the phenotype and reported dopaminergic dysfunction in torsinA-mediated dystonia.

219. Parkin co-regulated gene (Pacrg) is an axonemal protein involved in sperm tail and ependymal cell function and is a candidate primary ciliary dyskinesia gene

A leading cause of male infertility is genetic variation in genes required for sperm formation or function. Considerable evidence suggests PACRG is involved in spermiogeneis. The loss of Pacrg function causes infertility in mice (Lorenzetti et al. 2004) and we have shown an association between variability in the 5′ untranslated region of PACRG and human male infertility (Wilson et al. in preparation). Evidence from studies in C.reinhardtii and T.brucei indicate Pacrg is crucial for axonome formation and microtubule stability. To assess this possibility in mammals, we generated and characterised Pacrg knockout (Quaking viable, Qkv), wildtype and Pacrg transgenic mice (Qkv-Tg). Using confocal and immunoelectron microscopy we showed that Pacrg was localised to the axonemal microtubule doublets of sperm, tracheal and ependymal cilia. The absence of Pacrg was associated with compromised sperm flagella formation and MRI analyses revealed the occurrence of hydrocephalus. Specifically, Qkv mice showed an inward expansion of the lateral ventricles, resulting in a significant reduction in distance between ventricles (1.0 ± 0.6 mm, mean ± s.d., n = 5) and a ~250% increase in ventricle area (70 ± 13 arbitrary units, mean ± s.d., n = 5) compared with wildtype littermates (1.38 ± 0.09 mm; area 26 ± 12, n = 3). Transgenic expression of Pacrg was necessary and sufficient to correct the hydrocephalus (1.45 ± 0.05 mm; area 26 ± 9, n = 2) and infertility phenotypes (evidenced by daily sperm counts and litter sizes). In conclusion, we have shown Pacrg is a novel axoneme associated protein in a subset of motile cilia/flagella and loss of Pacrg function results in spermiogenic defects and hydrocephalus in mice. Further, we have shown that variations in the human PACRG promoter are a risk factor in human male infertility. Collectively these data suggest PACRG is a candidate gene in the human syndrome of primary ciliary dyskinesia. (1) Lorenzetti D, Bishop CE, Justice MJ. 2004. Deletion of the Parkin coregulated gene causes male sterility in the quaking (viable) mouse mutant. Proc Natl Acad Sci U S A 101(22):8402–8407

Quality of life in Friedreich ataxia: what clinical, social and demographic factors are important?

The aim of this study was to examine the impact of Friedreich ataxia (FRDA) on quality of life (QOL) using a generic tool to explore factors potentially associated with health status. Sixty-three individuals with genetically confirmed FRDA, self completed the Medical Outcomes Study 36 item Short Form Health Survey Version 2 (SF-36V2) and were assessed using the FRDA Rating Scale. Disease-specific, demographic, and social characteristics were also recorded. SF-36V2 results were compared with Australian population norms. Sample subgroups of disease severity and age at disease onset were reviewed. Physical and mental component summaries were examined in relation to clinical and social characteristics using multiple linear regression. QOL is significantly worse in individuals with FRDA compared with population norms. Those with severe disease did not perceive a lower QOL than those with mild or moderate disease except in their physical functioning. A later age of onset and increased disease severity were negatively associated with physical QOL, whilst, increased disease duration was positively associated with mental QOL. There were limitations associated with the use of SF-36V2 in the FRDA population. Further exploration of health-related QOL and FRDA may benefit from the use of a more appropriate generic tool.

How is disease progress in Friedreich's ataxia best measured? A study of four rating scales

BACKGROUND

Friedreich's ataxia (FRDA), the most common genetic cause of ataxia, is characterised by progressive neurodegeneration and cardiomyopathy. Initial treatments are likely to slow progression rather than reverse morbidity. An appropriate and sensitive scale to measure disease progress is critical to detect the benefit of treatments.

OBJECTIVE

To compare the Friedreich Ataxia Rating Scale (FARS) with other scales proposed as outcome measures for FRDA.

METHODS

76 participants were assessed with the FARS and the International Cooperative Ataxia Rating Scale (ICARS) and 72 of these participants were also assessed with the Functional Independence Measure and the Modified Barthel Index. 43 participants had repeat measures at an interval of 12 months. Sensitivity and responsiveness were assessed using the effect size for each measure and the sample size required for a placebo-controlled clinical trial.

RESULTS

The FARS showed a high correlation with the other three measures. A significant change in the score over 12 months was detected by the FARS, the International Cooperative Ataxia Rating Scale and the Functional Independence Measure. The FARS had the greatest effect size and requires fewer patients for an equivalently powered study.

CONCLUSIONS

Of the scales assessed, the FARS is the best to use in clinical trials of FRDA. This is based on effect size, and power calculations that show that fewer participants are required to demonstrate the same effect of an intervention. Further work is required to develop more sensitive and responsive instruments.

Newborn screening for mucopolysaccharidoses: opinions of patients and their families

We have conducted a study to assess the opinions of parents of individuals with mucopolysaccharidoses (MPS) and adults with MPS regarding newborn screening (NBS) for this condition, as testing is now technically possible. A questionnaire including a number of hypothetical clinical scenarios about NBS for MPS was distributed to members of MPS support groups from United States and Australia. Questionnaires were returned by 249 members of the US (40% response) and Australian (38% response) support groups. Eleven respondents were adults with MPS and the rest were parents of individuals with MPS. Eighty-six percent of respondents indicated that they would have wanted NBS for their own children. Ninety-seven percent supported the use of NBS for MPS in situations where early treatment that favorably impacts on disease outcome is available, 87% supported NBS when a severe form of MPS was diagnosed, but no treatment is available that improves the long-term outcome and 84% supported NBS for mild MPS where no disease-modifying treatment is available. The most common reason cited in support of NBS was that NBS could avoid a delay in diagnosis and the accompanying distress that delayed diagnosis created. This study has identified strong support for the introduction of NBS for MPS from this group. Psychosocial benefits of screening may outweigh potential harms.

Predictive genetic testing in young people for adult-onset conditions: where is the empirical evidence?

Predictive genetic testing in young people for severe, adult-onset conditions is advised against in current guidelines. Despite this, there has been considerable debate regarding the issue. Some perceive such testing as too potentially harmful to allow. Others perceive it as an opportunity for the promotion of benefit, an opportunity even for the prevention of harm. The only way to resolve this theoretical debate is to collect empirical data related to the effects of such testing when it occurs. However, more than 15 years after the debate began, there is virtually no such empirical evidence available. The reasons for this lack of evidence appear to relate to the rarity of such testing, which when it occurs is not studied systematically. Additionally, clinicians performing such tests may feel vulnerable in sharing the outcomes, given that such testing is contrary to current recommendations. We propose a way forward that entails the provision of tests to mature minors, where clinicians deem this appropriate. These tests should be performed as part of an international research collaboration, facilitated by one leading group.

Educational outcomes of a workplace screening program for genetic susceptibility to hemochromatosis

Education is an essential component of a genetic screening program. Knowledge outcomes were measured after large-scale workplace education and screening for genetic susceptibility to hereditary hemochromatosis. The aim was to assess knowledge of concepts presented, impact of mode of delivery, and knowledge retention. Education in a group setting was delivered via oral or video presentation and knowledge assessed using self-administered questionnaires at baseline, 1 month, and 12 months. Over 60% of 11 679 participants correctly answered all questions at baseline, scoring higher with clinical concepts (disease etiology and treatment) than genetic concepts (penetrance and genetic heterogeneity). Revising the education program significantly increased correct responses for etiology (p < 0.002), whilst modifying the knowledge assessment tool significantly increased correct responses for etiology (p < 0.001) and gene penetrance (p < 0.001). For three of the four concepts assessed, use of video was as effective as oral presentation for knowledge outcomes. A significantly higher proportion of those at increased risk of disease (n = 44) responded correctly at 12 months than did controls (n = 82; p = 0.011 for etiology, p = 0.002 for treatment and p = 0.003 for penetrance). Hence, genetic screening can be successfully offered in a group workplace setting, with participants remembering clinical concepts better than genetic concepts up to 1 year later.

Spinocerebellar ataxia type 14: study of a family with an exon 5 mutation in the PRKCG gene

We report our observations in an Australian family with spinocerebellar ataxia type 14 (SCA 14). We describe a novel mutation in exon 5 of the PRKCG gene, altering a highly conserved cysteine to a phenylalanine at codon 150, and record the detailed clinical observations in six affected family members.

Sleep disturbance in Sanfilippo syndrome: a parental questionnaire study

AIMS

To determine the incidence, manifestations, and best management of sleep disturbance in Sanfilippo syndrome (mucopolysaccharidosis (MPS) type III).

METHODS

Families were ascertained through the MPS societies of Australasia, the UK, and the USA. Questionnaires were sent by mail and were answered anonymously. Identical questions regarding sleep disturbance were asked about unaffected siblings to provide control data. Sleep disturbance was quantified by a total sleep disturbance score.

RESULTS

A total of 141 responses were received; 91.5% of children with Sanfilippo syndrome had sleep disturbance and this was significantly higher than for their unaffected sibs; 77.5% of parents had used medication for this problem, with melatonin and antihistamines being most commonly used. Melatonin and benzodiazepines were reported as the most efficacious. Many different environmental modifications had been employed for this problem and some parents reported success with behavioural therapies.

CONCLUSIONS

Sleep disturbance is common, severe, and difficult to manage in Sanfilippo syndrome. Based on the parental responses and its safety profile, melatonin is the first line drug that should be tried. Behavioural therapy should be tried in all with Sanfilippo syndrome and sleep disturbance.

Ethical considerations in presymptomatic testing for variant CJD

Variant Creutzfeldt-Jakob disease (vCJD) is a fatal, transmissible, neurodegenerative disorder for which there is currently no effective treatment. vCJD arose from the zoonotic spread of bovine spongiform encephalopathy. There is now compelling evidence for human to human transmission through blood transfusions from presymptomatic carriers and experts are warning that the real epidemic may be yet to come. Imperatives exist for the development of reliable, non-invasive presymptomatic diagnostic tests. Research into such tests is well advanced. In this article the ethical implications of the availability of these tests are elaborated and comparisons drawn with predictive genetic testing for Huntington's disease and screening for HIV. Paramount to considerations is the issue of whom to test, weighing up respect for personal autonomy against obligations to benefit and protect society. A paradigm is proposed similar to that used for HIV screening but with unique features: compulsory testing of all blood/organ donors and individuals undergoing surgery or invasive procedures who have a significant risk of disease transmission.

Use of community genetic screening to prevent HFE-associated hereditary haemochromatosis

HFE-associated hereditary haemochromatosis is a recessive, iron-overload disorder that affects about one in 200 north Europeans and that can be easily prevented. However, genetic screening for this disease is controversial, and so we assessed whether such screening was suitable for communities. Cheek-brush screening for the Cys282Tyr HFE mutation was offered to individuals in the workplace. Outcomes were assessed by questionnaires before and after testing. 11,307 individuals were screened. We recorded no increase in anxiety in individuals who were homozygous for the Cys282Tyr mutation or non-homozygous. Self-reported tiredness before testing was significantly higher in homozygous participants than in non-homozygous participants (chi2 test, p=0.029). Of the 47 homozygous individuals identified, 46 have taken steps to treat or prevent iron accumulation. Population genetic screening for HFE-associated hereditary haemochromatosis can be practicable and acceptable.

Genetic susceptibility screening in schools: attitudes of the school community towards hereditary haemochromatosis

Carrier screening to provide reproductive options has been offered to students in the school setting for a number of years; however, genetic susceptibility screening for disease predisposition has not been introduced to the school community. Experience has shown that the success of a population-based programme relies on the community's acceptance. Therefore, we sought to establish the Australian secondary school community's attitudes towards genetic susceptibility screening in schools, with hereditary haemochromatosis as the model condition with an available prevention. School students, aged 15-18 (n = 748), completed a questionnaire immediately before and following an oral educational presentation. Their parents (n = 179) and staff (n = 89) received written information and returned a questionnaire by post. Semi-structured interviews were with Government representatives. Attitudes towards genetic screening in schools and knowledge of genetic and clinical features of haemochromatosis, as well as the likelihood of accepting a genetic susceptibility test for haemochromatosis, were all measured. Participants were positive about genetic screening for disease susceptibility in schools. Their knowledge was high following education with no significant differences between participants of each group. Sixty-eight percent of students would be likely to have the test if it were offered, with parents and staff, indicating that they would like the students to be offered a test, on average. Genetic susceptibility screening in schools is a novel concept. The results of our study indicate that it could be a public health success with the support of the community.

A homozygous HAMP mutation in a multiply consanguineous family with pseudo-dominant juvenile hemochromatosis

Juvenile hemochromatosis (JH) is an autosomal recessive condition that leads to significant morbidity due to early onset systemic iron overload. The majority of families with JH link to chromosome 1q and were recently found to have mutations in the HFE2 gene encoding hemojuvelin; however, several JH families have been reported to have mutations in the HAMP gene encoding hepcidin. Here, we report a multiply consanguineous family with a father and daughter showing iron overload consistent with JH. Sequence analysis of HAMP revealed homozygosity for amino acid substitution C78T due to a c.233G > A mutation. This mutation disrupts one of eight highly conserved cysteines that are believed to be critical for the function of the active enzyme. This finding adds support to the importance of the role of these conserved cysteines in the activity of hepcidin.

Implementation of HaemScreen, a workplace-based genetic screening program for hemochromatosis

There is debate as to whether community genetic screening for the mutation(s) causing hereditary hemochromatosis (HH) should be implemented, due to issues including disease penetrance, health economic outcomes, and concerns about community acceptance. Hemochromatosis is a common preventable iron overload disease, due in over 90% of cases to C282Y homozygosity in the HFE gene. We are, therefore, piloting C282Y screening to assess understanding of genetic information and screening acceptability in the workplace setting. In this program, HaemScreen, education was by oral or video presentation in a group setting. C282Y status was assessed by polymerase chain reaction (PCR) and melt-curve analysis on DNA obtained by cheek-brush sampling. Of eligible participants, 5.8% (1.5-15.8%) attended information and screening sessions, of whom 97.7% (5571 individuals) chose to be tested. Twenty-two C282Y (1 : 253) homozygotes were identified and offered clinical follow-up. There were 638 heterozygotes (1 : 8.7). The determinants for participation have been analyzed in terms of the principles outlined in the Health Belief Model. Widespread screening for HH is readily accepted in a workplace setting, and a one-to-many education program is effective. The level of participation varies greatly and the advertizing and session logistics should be adapted to the specific features of each workplace.

Growth, behavior, and clinical findings in 27 patients with Kabuki (Niikawa-Kuroki) syndrome

This study was undertaken to document the phenotype of Kabuki (Niikawa-Kuroki) syndrome in patients from Australia and New Zealand, with particular emphasis on growth patterns, behavior, and relationship between head circumference and intellectual level. Data on 27 children and adults with Kabuki (Niikawa-Kuroki) syndrome from Australia and New Zealand were collected by questionnaire and clinical assessment. The patients ranged in age from 7 months to 36 years with a mean age of 7 years and 2 months. The mean age at diagnosis was 3(5/6) years, but in most cases, the facial phenotype was evident from infancy. The minimum birth prevalence was calculated at 1 in 86,000. Three of our patients died. Parents reported a behavior phenotype characterized by an excellent long-term memory and avoidance of eye contact. No correlation was found between head circumference and severity of intellectual disability. Eight of 14 patients over the age of 5 years were overweight or obese. Six of these eight patients had failure to thrive in infancy. One patient developed insulin-dependent diabetes mellitus in adolescence. Some individuals with Kabuki (Niikawa-Kuroki) syndrome show a characteristic growth profile with failure to thrive in infancy progressing to obesity or overweight in middle childhood or adolescence. A behavior phenotype was noted which requires further investigation. Head size is not a predictor of degree of intellectual disability.

Evaluation of a Tay-Sachs disease screening program

Tay-Sachs Disease (TSD) is an autosomal recessive neurodegenerative disorder. TSD is prevalent in the Ashkenazi Jewish population, and carrier screening programs have been implemented worldwide in these communities. A screening program initiated in 1997 involving the Melbourne Jewish community (Australia) incorporated education, counselling and carrier testing of high-school students aged 15 to 18 years. This study aimed to assess the participation rates, level of knowledge obtained and predicted feelings and attitudes of the students involved. Seven hundred and ten students participated, there was a 67% uptake for testing with a carrier rate of 1 in 28 determined. The level of knowledge of the students following education was high and of relative importance in regard to decision making, as were their feelings and attitudes about genetic testing for carrier status. A significant impediment to test uptake was the need for blood sampling, resulting in a recommendation for the introduction of DNA analysis on cheek brush samples. The evaluation of this program has given a wider scope for further development as well as providing valuable information for the implementation of community screening programs.

Sleep disturbance in mucopolysaccharidosis type III (Sanfilippo syndrome): a survey of managing clinicians

Sanfilippo syndrome (mucopolysaccharidosis type III) is the commonest mucoploysaccharidosis. It causes neurodegeneration with often profound sleep and behavioral disturbance. Management of the sleep disturbance is difficult and inconsistent. In this study, we surveyed clinicians with particular expertise in the management of individuals with mucopolysaccharidoses. We found that sleep problems are almost universal in this patient population and that no one treatment is consistently viewed as beneficial. Among the clinicians surveyed, melatonin is reported as the medication most likely to be of benefit. Benzodiazepines, chloral hydrate, antihistamines and antipsychotic agents are overall reported as less efficacious. The major side-effect of the medications as a group was reported to be daytime somnolence. Based on this study, recommendations are given regarding the approach to sleep disturbance in Sanfilippo syndrome.

Genetic factors in athetoid cerebral palsy

Within the cerebral palsy syndromes, athetosis is most commonly causally associated with serious perinatal complications. Genetic factors are thought to play a lesser role, although the risk of recurrence in siblings has been suggested to be as high as 10%. We have conducted a clinical study of 22 subjects with a diagnosis of athetoid cerebral palsy and a review of the literature aiming to identify instances of familial recurrence of athetoid cerebral palsy. The birth history, family history, and previous investigations of subjects with athetoid cerebral palsy were studied and subjects were clinically examined for evidence of an underlying genetic etiology. Factors suggesting a genetic cause were specifically sought, such as advanced paternal age, progression of symptoms, and associated congenital abnormalities. No subjects in the study group had similarly affected relatives, and additional features suggesting a genetic cause were not observed. A literature search identified 16 instances of familial recurrence of athetoid cerebral palsy. Familial cases were typically associated with significant spasticity, microcephaly, intellectual disability, seizures, and a lack of history of birth asphyxia, and most could be explained by either autosomal-recessive or X-linked-recessive inheritance. The genetic contribution to athetoid cerebral palsy is small, with an overall risk of recurrence in siblings of about 1%. This risk is lower than previously suggested in the literature.

New variant of familial cerebellar ataxia with hypergonadotropic hypogonadism and sensorineural deafness

Cerebellar ataxia and hypergonadotropic hypogonadism comprise a rare and presumably heterogeneous association. Inheritance in most cases appears to be autosomal recessive, and associated features include deafness, intellectual impairment, and neuropathy. Typically, onset of ataxia is in the first decade and hypogonadism results in primary amenorrhoea in females. We describe two sisters with a previously undescribed pattern of adult onset progressive cerebellar ataxia and secondary amenorrhoea due to hypergonadotropic hypogonadism. Sensorineural deafness with vestibular hypofunction and peripheral sensory impairment were also present, and intellect was normal. Onset of neurological symptoms was in the third decade, with secondary amenorrhoea occurring at the ages of 16 and 32 years, respectively. The association of ataxia and hypergonadotropic hypergonadism has been classified both as a variant of Holmes type ataxia and as a variant of Perrault syndrome, but we suggest the use of a separate category of ataxia with hypergonadotropic hypogonadism.

Friedreich ataxia: an overview

Friedreich ataxia, an autosomal recessive neurodegenerative disease, is the most common of the inherited ataxias. The recent discovery of the gene that is mutated in this condition, FRDA, has led to rapid advances in the understanding of the pathogenesis of Friedreich ataxia. About 98% of mutant alleles have an expansion of a GAA trinucleotide repeat in intron 1 of the gene. This leads to reduced levels of the protein, frataxin. There is mounting evidence to suggest that Friedreich ataxia is the result of accumulation of iron in mitochondria leading to excess production of free radicals, which then results in cellular damage and death. Currently there is no known treatment that alters the natural course of the disease. The discovery of the FRDA gene and its possible function has raised hope that rational therapeutic strategies will be developed.

Clinical and genetic study of Friedreich ataxia in an Australian population

Friedreich ataxia is an autosomal recessive disorder caused by mutations in the FRDA gene that encodes a 210-amino acid protein called frataxin. An expansion of a GAA trinucleotide repeat in intron 1 of the gene is present in more than 95% of mutant alleles. Of the 83 people we studied who have mutations in FRDA, 78 are homozygous for an expanded GAA repeat; the other five patients have an expansion in one allele and a point mutation in the other. Here we present a detailed clinical and genetic study of a subset of 51 patients homozygous for an expansion of the GAA repeat. We found a correlation between the size of the smaller of the two expanded alleles and age at onset, age into wheelchair, scoliosis, impaired vibration sense, and the presence of foot deformity. There was no significant correlation between the size of the smaller allele and cardiomyopathy, diabetes mellitus, loss of proprioception, or bladder symptoms. The larger allele size correlated with bladder symptoms and the presence of foot deformity. The duration of disease is correlated with wheelchair use and the presence of diabetes, scoliosis, bladder symptoms and impaired proprioception, and vibration sense but no other complications studied.

G130V, a common FRDA point mutation, appears to have arisen from a common founder

Friedreich ataxia (FRDA) is the most common inherited ataxia. About 98% of mutant alleles have an expansion of a GAA trinucleotide repeat in intron 1 of the affected gene, FRDA. The other 2% are point mutations. Of the 17 point mutations so far described, three appear to be more common. One of these is the G130V mutation in exon 4 of FRDA. G130V, when present with an expanded GAA repeat on the other allele, is associated with an atypical FRDA phenotype. Haplotype analysis was undertaken on the four families who have been described with this mutation. The results suggest a common founder for this mutation. Although marked differences in extragenic marker haplotypes were seen in one family, similar intragenic haplotyping suggests the same mutation founder for this family with the differences explicable by two recombination events.

Direct evidence that mitochondrial iron accumulation occurs in Friedreich ataxia

Friedreich ataxia (FRDA) is due to mutations in the FRDA gene (FRDA). When the gene homologous to FRDA is knocked out in yeast, there is accumulation of iron in mitochondria and reduced respiratory function. So far, there is only indirect evidence to support the hypothesis that FRDA is due to accumulation of mitochondrial iron leading to increased production of free radicals. We show here that mitochondrial iron is significantly higher in fibroblasts from patients with FRDA than in control fibroblasts. This is the first direct evidence that the findings in yeast are reproducible in cells from patients with FRDA.

Directly inherited partial trisomy of chromosome 6p identified in a father and daughter by chromosome microdissection

Cytogenetic analysis of a 4 year old girl with developmental delay and dysmorphic features showed extra chromosomal material of unknown origin on 20p (46,XX,add(20)(p13)). Familial chromosome studies showed direct inheritance of add(20)(p13) from the father, who had a similar, albeit milder, phenotype. Fibroblast chromosome studies of the father showed no karyotype mosaicism. The additional material could not be identified on the basis of the G banding pattern owing to its small size and ambiguous banding pattern. Chromosome microdissection of the unknown material was performed, the DNA was amplified and labelled using degenerate oligonucleotide primed polymerase chain reaction (DOP-PCR) and reverse painted to the proband's cells to show the karyotype 46,XX,der(20)t(6;20) (p23;p13), conferring partial trisomy 6p and presumed partial monosomy for 20p. Chromosome microdissection has made possible the first reported case of directly inherited partial trisomy 6p.

Persistent truncus arteriosus in monozygotic twins: case report and literature review

We report on a pair of monozygotic twins with persistent truncus arteriosus. They had no evident clinical signs of DiGeorge syndrome. Pathologic examination of the placenta and DNA analysis in chromosomes 7, 8, and 15 was consistent with monozygosity. Fluorescence in situ hybridization test was negative for chromosome 22q11 microdeletion. Family history revealed a female cousin with tetralogy of Fallot. The isolated presence of this conotruncal abnormality in monozygotic twins is extremely rare. The genetic considerations are discussed.