Converging pharmacological and genetic evidence indicates a role for steroid sulfatase in attention

The influence of sex-linked genetic mechanisms on attention and impulsivity

It is now generally agreed that there are inherent sex differences in healthy individuals across a number of neurobiological domains (including brain structure, neurochemistry, and cognition). Moreover, there is a burgeoning body of evidence highlighting sex differences within neuropsychiatric populations (in terms of the rates of incidence, clinical features/progression, neurobiology and pathology). Here, we consider the extent to which attention and impulsivity are sexually dimorphic in healthy populations and the extent to which sex might modulate the expression of disorders characterised by abnormalities in attention and/or impulsivity such as attention deficit hyperactivity disorder (ADHD), autism and addiction. We then discuss general genetic mechanisms that might underlie sex differences in attention and impulsivity before focussing on specific positional and functional candidate sex-linked genes that are likely to influence these cognitive processes. Identifying novel sex-modulated molecular targets should ultimately enable us to develop more effective therapies in disorders associated with attentional/impulsive dysfunction.

Steroid sulfatase inhibitors: a review covering the promising 2000-2010 decade

The steroid sulfatase (STS) plays a major role in the regulation of steroid hormone concentrations in several human tissues and target organs and therefore, represents an interesting target to regulate estrogen and androgen levels implicated in different diseases. In this review article, the emphasis is put on STS inhibitors reported in the fruitful 2000-2010 decade, which consolidated the first ones that were previously developed (1990-1999). The inhibitors reviewed are divided into four categories according to the fact that they are sulfamoylated or not or that they have a steroid nucleus or not. Other topics such as function, localization, structure and mechanism as well as applications of STS inhibitors are also briefly discussed to complement the information on this crucial steroidogenic enzyme and its inhibitors.

Association of salivary dehydroepiandrosterone levels and symptoms in patients with attention deficit hyperactivity disorder during six months of treatment with methylphenidate

This prospective study aimed to determine whether salivary levels of dehydroepiandrosterone (DHEA) in patients with attention deficit hyperactivity disorder (ADHD) change significantly during 6 months of treatment with methylphenidate (MPH), and to investigate long-term relationship between these levels and ADHD symptoms. Fifty ADHD patients aged between 6 and 12 years, and 50 age- and gender-matched healthy subjects were recruited. ADHD patients were prescribed oral MPH with a dose range of 5-15 mg/day at the discretion of the psychiatrist. DHEA levels were determined from saliva samples collected from both ADHD patients and healthy subjects at pretreatment and 1, 3, and 6 months from pretreatment visit. ADHD symptoms were evaluated with the Swanson, Nolan, and Pelham, Version IV Scale for ADHD and the ADHD Rating Scale, and computerized Continuous Performance Test (CPT). The results showed that salivary DHEA levels significantly increased in ADHD patients during the 6-month course of methylphenidate treatment, but the DHEA levels did not significantly change in the untreated healthy group during the 6-month period of natural observation. For the longitudinal observation, among ADHD patients, the salivary DHEA levels were independently correlated with distraction and impulsivity performance in the CPT, but not correlated with inattention and hyperactivity in the clinical ADHD symptoms. Whether DHEA exerts effects on neurocognitive functions as mediators or independently of MPH warrants further investigation.

ADHD and genetic syndromes

A high rate of Attention Deficit/Hyperactivity Disorder (ADHD)-like characteristics has been reported in a wide variety of disorders including syndromes with known genetic causes. In this article, we review the genetic and the neurobiological links between ADHD symptoms and some genetic syndromes such as: Fragile X Syndrome, Neurofibromatosis 1, DiGeorge Syndrome, Tuberous Sclerosis Complex, Turner Syndrome, Williams Syndrome and Klinefelter Syndrome. Although each syndrome may arise from different genetic abnormalities with multiple molecular functions, the effects of these abnormalities may give rise to common effects downstream in the biological pathways or neural circuits, resulting in the presentation of ADHD symptoms. Early diagnosis of ADHD allows for earlier treatment, and has the potential for a better outcome in children with genetic syndromes.

Salivary dehydroepiandrosterone, but not cortisol, is associated with attention deficit hyperactivity disorder

OBJECTIVES

The purposes of this study were to determine whether salivary levels of dehydroepiandrosterone (DHEA) and cortisol are associated with attention deficit hyperactivity disorder (ADHD) or correlated with performance on the Continuous Performance Test (CPT).

METHODS

Fifty ADHD patients and 50 age- and gender-matched controls aged between 6 and 12 years were included in this cross-sectional study. DHEA and cortisol levels were determined from saliva samples collected by the passive drool method at 08:00 h. ADHD patients subsequently performed a computerized Continuous Performance Test (CPT). ADHD symptoms were evaluated with the Swanson, Nolan, and Pelham, Version IV Scale for ADHD (SNAP-IV), completed by the patients' parents, and with the ADHD Rating Scale (ADHD-RS), administered by a child psychiatrist.

RESULTS

Saliva DHEA levels and DHEA/cortisol ratios differed significantly between ADHD patients and controls. Among ADHD patients, saliva DHEA levels and DHEA/cortisol ratios were independently correlated with composite scores of CPT distractibility and CPT impulsivity. Basal levels of cortisol were not significantly associated with ADHD.

CONCLUSIONS

DHEA, but not the cortisol basal level, may be a biological laboratory marker for ADHD, particularly for performance on the CPT. Both the causal relationship between DHEA and ADHD and the role of DHEA in treating ADHD require further investigation.

Steroid sulfatase is a potential modifier of cognition in attention deficit hyperactivity disorder

Deletions encompassing the X-linked STS gene (encoding steroid sulfatase) have been observed in subjects with neurodevelopmental disorders, including attention deficit hyperactivity disorder (ADHD). Recently, two single nucleotide polymorphisms (SNPs) within STS (rs12861247 and rs17268988) have been reported to be associated with ADHD risk and inattentive symptoms in ADHD, respectively. Using a UK sample of ADHD subjects (aged 5-18 years), we tested the hypothesis that rs12861247 is associated with ADHD risk using a case-control approach (comparing 327 ADHD cases with 358 male controls from the Wellcome Trust Case Control Consortium). Using a subset of males from the ADHD sample, we also examined whether variation within STS is associated with symptomatology/cognitive function in ADHD. We then tested whether SNPs associated with cognitive function in ADHD were also associated with cognitive function in healthy male subjects using a German sample (n = 143, aged 18-30 years), and whether STS was expressed in brain regions pertinent to ADHD pathology during development. We did not replicate the previously identified association with rs12861247. However, in ADHD males, variation at rs17268988 was associated with inattentive symptoms, while variation within STS was significantly associated with performance on three cognitive measures. Three SNPs associated with cognitive function in ADHD males were not associated with cognitive function in healthy males. STS was highly expressed in the developing cerebellar neuroepithelium, basal ganglia, thalamus, pituitary gland, hypothalamus and choroid plexus. These data suggest that genetic variants affecting STS expression and/or activity could influence the function of brain regions perturbed in ADHD.

Polymorphisms of the steroid sulfatase (STS) gene are associated with attention deficit hyperactivity disorder and influence brain tissue mRNA expression

Previous studies in animals and humans have implicated the X-chromosome STS gene in the etiology of attentional difficulties and attention deficit hyperactivity disorder (ADHD). This family based association study has fine mapped a region of the STS gene across intron 1 and 2 previously associated with ADHD, in an extended sample of 450 ADHD probands and their parents. Significant association across this region is demonstrated individually with 7 of the 12 genotyped SNPs, as well as an allele specific haplotype of the 12 SNPs. The over transmitted risk allele of rs12861247 was also associated with reduced STS mRNA expression in normal human post-mortem frontal cortex brain tissue compared to the non-risk allele (P = 0.01). These results are consistent with the hypothesis arising from previous literature demonstrating that boys with deletions of the STS gene, and hence no STS protein are at a significantly increased risk of developing ADHD. Furthermore, this study has established the brain tissue transcript of STS, which except from adipose tissue, differs from that seen in all other tissues investigated. © 2010 Wiley-Liss, Inc.

Interstitial microduplication of Xp22.31: Causative of intellectual disability or benign copy number variant?

The use of comparative genomic hybridization (CGH) and single nucleotide polymorphism (SNP) arrays has dramatically altered the approach to identification of genetic alterations that can explain intellectual disability and /or congenital anomalies. However, the discovery of numerous copy number changes with benign or unknown clinical significance has made interpretation problematic. Submicroscopic duplication of Xp22.31 has been reported as either a possible cause of intellectual disability and/or developmental delay or a benign variant. Here we report 29 individuals with the microduplication found as part of microarray analysis of 7793 samples submitted to an international group of 13 clinical laboratories. The referral reasons varied and included developmental delay, intellectual disability, autism, dysmorphic features and/or multiple congenital anomalies. The size of the Xp22.31 duplication varied between 149 kb and 1.74 Mb and included the steroid sulfatase (STS) gene with the male to female ratio of 0.7. Duplication within this segment is seen at a frequency of 0.15% in a healthy control population, whereas a frequency of 0.37% was observed in our cohort of individuals with abnormal phenotypes. We present a detailed comparison of the breakpoints, inheritance, X-inactivation and clinical phenotype in our cohort and a review of the literature for a total of 41 patients. To date, this report is the largest compilation of clinical and array data regarding the microduplication of Xp22.31 and will serve to broaden the knowledge of regions involving copy number variation (CNV).

The Role of the Y Chromosome in Brain Function

In mammals, sex differences are evident in many aspects of brain development, brain function and behaviour. Ultimately, such differences must arise from the differential sex chromosome complements in males and females: males inherit a single X chromosome and a Y chromosome, whilst females inherit two X chromosomes. One possible mechanism for sexual differentiation of the brain is via male-limited expression of genes on the small Y chromosome. Many Y-linked genes have been implicated in the development of the testes, and therefore could theoretically contribute to sexual differentiation of the brain indirectly, through influencing gonadal hormone production. Alternatively, Y-linked genes that are expressed in the brain could directly influence neural masculinisation. The present paper reviews evidence from human genetic studies and animal models for Y-linked effects (both direct and indirect) on neurodevelopment, brain function and behaviour. Besides enhancing our knowledge of the mechanisms underlying mammalian neural sexual differentiation, studies geared towards understanding the role of the Y chromosome in brain function will help to elucidate the molecular basis of sex-biased neuropsychiatric disorders, allowing for more selective sex-specific therapies.