Methylation Dynamics on 5′-UTR of DAT1 Gene as a Bio-Marker to Recognize Therapy Success in ADHD Children

Abstract

Attention-deficit/hyperactivity disorder (ADHD), a neuropsychiatric condition characterized by inattention, hyperactivity, and impulsivity, afflicts 5% of children worldwide. Each ADHD patient presents with individual cognitive and motivational peculiarities. Furthermore, choice of appropriate therapy is still up to clinicians, who express somewhat qualitative advice on whether a child is being successfully cured or not: it would be more appropriate to use an objective biomarker to indicate whether a treatment led to benefits or not. The aim of our work is to search for such clinical biomarkers. We recruited 60 ADHD kids; psychopathological scales were administered at recruitment and after six weeks of therapy. Out of such a cohort of ADHD children, we rigorously extracted two specific subgroups; regardless of the initial severity of their disease, we compared those who obtained the largest improvement (ΔCGAS > 5) vs. those who were still characterized by a severe condition (CGAS < 40). After such a therapy, methylation levels of DNA extracted from buccal swabs were measured in the 5’-UTR of the DAT1 gene. CpGs 3 and 5 displayed, in relation to the other CpGs, a particular symmetrical pattern; for “improving” ADHD children, they were methylated together with CpG 2 and CpG 6; instead, for “severe” ADHD children, they accompanied a methylated CpG 1. These specific patterns of methylation could be used as objective molecular biomarkers of successful cures, establishing if a certain therapy is akin to a given patient (personalized medicine). Present data support the use of post-therapy molecular data obtained with non-invasive techniques.

DAT1 5′-Un-Translated-Region Methylation Patterns as Bio-Markers of ADHD Psycho-Pathology: Contribution to Disease Prognosis and to Monitoring of a Successful Therapy

“…In contrast, our studies do not analyze mRNA expression and protein activity levels of (de)methylation enzymes, which unfortunately makes it quite difficult to draw more definitive conclusions. However, there are several other limiting factors that must be considered in both the studies here compared [8,10]:…”

“…The main characteristics of the two studies [ 8 , 10 ] are summarized in Table 1 . Both were conducted on Italian children aged 6 to 11/12 years.…”

“…This commentary addresses recent advances in the use of molecular biomarkers for providing an objective account of the clinical situation in patients suffering from a very common developmental neuropsychiatric disorder, such as the attention-deficit/hyperactivity disorder (ADHD). Recent data from the group of Marzilli and Cimino as well as the group of Carpentieri and Adriani [ 8 , 9 , 10 ] suggest that a new biomarker has emerged from the dopamine transporter SLC6A3 gene, known as DAT1 . Taken together, the data reviewed here may be relevant to the therapeutic plan supporting children with ADHD.…”

“…The first study, by Marzilli and Cimino [ 8 ], addresses the correlation between methylation markers at specific CpG loci and key symptoms suggestive of ADHD; the other two works by Carpentieri and Adriani [ 9 , 10 ] address a purely prognostic intent, namely whether the analysis of methylation can help physicians to establish and monitor an effective treatment plan. According to these two\three papers, when merging the various details about the patient and her/his family, based on the type of methylation pattern observed, we could eventually be able to predict the initial severity and treatment resistance of ADHD and subsequently formulate individualized therapy.…”

“…Interestingly, the data for the heterozygous 9/10 subjects show that what really matters is whether the father in particular has transmitted the 9R or 10R DAT1 allele, as well as the quality of his relationship with his son/daughter. Overall, by comparing data from our three recent papers [ 9 , 10 , 14 ], this commentary proposes the use of epigenetic biomarkers for the diagnosis and/or prognosis of a prototypical externalizing disorder, such as ADHD, as well as internalizing psychopathological traits. The use of DAT1 methylation as a biomarker to detect ADHD symptoms, as well as internalizing and\or externalizing psycho-pathological traits, is also supported by other studies [ 15 , 16 , 17 , 18 ].…”