Laura Filonzi

Association of dopamine transporter and monoamine oxidase molecular polymorphisms with sudden infant death syndrome and stillbirth: new insights into the serotonin hypothesis

Recent findings demonstrated the role of neurotransmitters in the aetiopathogenesis of sudden unexpected deaths in infancy. Although genes involved in serotonin metabolism have been proposed as risk factors for sudden infant death syndrome (SIDS), the contribution of additional neurotransmitters and genes different from the serotonin transporter (SLC6A4, 5-HTT) has not been investigated. Considering the common metabolic pathway and synergism between dopamine and serotonin, the role of dopamine transporter (SLC6A3, DAT) and monoamine oxidase A (MAOA) genes in SIDS and stillbirth (sudden intrauterine unexplained death, SIUD) was investigated. Genotypes and allelic frequencies of DAT and MAOA were determined in 20 SIDS and five stillbirth cases and compared with 150 controls. No association was found between DAT polymorphisms and SIDS either at genotype (P = 0.64) or allelic (P = 0.86) level; however, a highly significant association was found between MAOA genotypes (P = 0.047) and alleles (P = 0.002) regulating different expression patterns (3R/3R vs 3.5R/3.5R + 4R/4R) in SIDS + SIUD and controls. Analysis of combined 5-HTTLPR (serotonin transporter linked polymorphic region)/MAOA genotypes revealed that frequency of L/L-4R/4R genotype combination was eightfold higher in SIDS + SIUD than in controls (P < 0.001). Findings are discussed considering the metabolic association among DAT, 5-HTT and MAOA with special emphasis on the linked action of 5-HTT/MAOA in regulating serotonin metabolism of SIDS and SIUD infants.

Confirmed association between monoamine oxidase A molecular polymorphisms and Sudden Infant Death Syndrome

We published in the February 2009 issue of Neurogenetics the article “Association of dopamine transporter and monoamine oxidase molecular polymorphisms with Sudden Infant Death Syndrome and stillbirth: new insights into the serotonin hypothesis” [1]. The aim of our work was to investigate the contribution of additional neurotransmitters and related genes, different from the serotonin transporter (SLC6A4, 5-HTT) in the development of SIDS and stillbirth. The main conclusion discussed in the paper was that the frequency of MAOA allele 4R (having increased transcriptional activity) was statistically higher in SIDS and stillbirth than in the Control Group. The conclusions in our article have recently been submitted to criticism by Klintschar and Heimbold [2] with a Letter to the Editor of Neurogenetics. We would kindly reply to their two main observations. The two authors have underlined that MAOA is an X chromosomal locus and the manuscript reported an inappropriate elaboration of allelic frequencies determined in 25 cases, 13 males and 12 females. We agree with their observation and we apologize for the involuntary oversight as we were aware that MAOA is an X-linked gene. The correct number of alleles was 37 instead of 50 erroneously reported in the paper. In relation to this we decided to reevaluate our results considering 37 alleles instead of 50. Results are reported in Table 1. It is noteworthy observing that conclusive data are exactly the same. The only difference regards the degree of statistical significance for allelic frequencies; in fact in the statistical data from the previous paper, the distribution of allele 3 (low transcriptional activity) vs. 3.5+4 (high activity) was highly significant (LR χ=9.60, P=0.002) while in this re-elaboration results remain significant (LR χ=5.52, P=

Evidence that polymorphic deletion of the glutathione S-transferase gene, GSTM1, is associated with esophageal atresia†

BACKGROUND Esophageal atresia (EA) is a life-threatening congenital condition whose etiology and pathogenesis are still poorly understood. An increasing trend of this pathology in some Italian regions suggests a possible interaction between xenobiotics and genes involved in detoxification processes during early embryonic development. For the first time polymorphisms of GSTM1, GSTT1, and GSTP1 genes were analyzed in association with EA. METHODS The study population consisted of 25 EA children, 50 unrelated healthy children, 20 of the EA childrens mothers, and 40 unrelated mothers. GSTM1 and GSTT1 null genotypes were identified by PCR amplification, and GSTP1 polymorphism was detected by RFLP analysis. RESULTS An association was found between homozygosity for the GSTM1 null genotype and EA in affected children (p = 0.0022) and their mothers (p = 0.022). No association was found between GSTT1 and GSTP1 polymorphisms and EA children or their mothers. CONCLUSIONS Results suggest that the GSTM1(-/-) null genotype may play an important role in the development of EA during early embryogenesis as a consequence of altered detoxification processes both in children and in the mothers. We hypothesize that GSTM1 allelic loss could be responsible for reduced or null catalytic activity in tissues exposed to amniotic fluid, and inefficient detoxification could be a trigger altering proliferation/apoptotic pattern of gut-trachea separation.

Serotonin Transporter Role in Identifying Similarities Between SIDS and Idiopathic ALTE

OBJECTIVE: Considering previous genetic studies on sudden infant death syndrome (SIDS) and the role of L/L serotonin transporter (5HTT) genotype and correlated genes monoamine oxidase A (MAOA) and dopamine transporter (DAT) in unexpected death, an investigation was carried out verifying their involvement in apparent life-threatening events (ALTE and idiopathic form [IALTE]), also assessing common molecular basis with SIDS. METHODS: Differential diagnoses in 76 ALTE infants, distinguishing ALTE from IALTE was elaborated by using clinical-diagnostic data. Genotypes/allelic frequencies of DAT, MAOA, and 5HTT were determined in ALTE and IALTE infants and compared with data obtained from 20 SIDS and 150 controls. RESULTS: No association was found between DAT polymorphisms and ALTE/IALTE groups either at the genotype or allelic level (P range .11–.94). MAOA genotypes and allele data comparison between ALTE and controls was not significant; IALTE data showed a tendency for genotypes (P = .09) and were statistically significant for alleles (P = .036); however, MAOA significance disappeared once the Bonferroni correction was applied. 5HTT polymorphisms in IALTE remarked the role of L/L genotype (P < .00001) and L (P < .00001), as previously demonstrated in SIDS. CONCLUSIONS: Considering correspondence between 5HTT and MAOA in IALTE and SIDS, we hypothesize that the 2 syndromes are different expressions of a common ethiopathogenesis. In particular, genetic data suggest SIDS events could derive from IALTE episodes occurred during sleep, and therefore out of parental control. Despite its functional role, results highlight the usefulness of 5HTT as a valuable tracer of SIDS risk in IALTE infants. Owing to the small sample size, the results are to be considered preliminary and should be reevaluated in an independent sample.

Molecular Barcoding of an Atypical Cyprinid Population Assessed by Cytochrome b Gene Sequencing

A fish population of the carp family Cyprinidae with atypical phenotypic characteristics was observed in one of the main catchments of the Pollino National Park, a valuable, protected area in southern Italy. In this area, the Italian roach Rutilus rubilio (Bonaparte, 1837), a native endemic fish of Tyrrhenean regions, has been introduced in sympatric conditions with Squalius squalus (Bonaparte, 1837) and Telestes muticellus (Bonaparte, 1837). A molecular investigation was carried out to assess the genetic identity of the population with a view to conservation. Direct sequencing of a cytochrome b gene fragment was performed based on 30 individuals of cyprinid fish with atypical phenotype, in addition to 30 S. squalus, 10 T. muticellus, and 30 R. rubilio pure individuals collected in different Italian regions, which served as reference samples. Multiple sequence alignments demonstrated that 50% of atypical-cyprinid haplotypes were maternally inherited from either S. squalus or R. rubilio. No contribution by T. muticellus was determined. Our results indicate an intergeneric hybridization event between S. squalus and R. rubilio, as a consequence of trans-introduction activities of alien species.

Genetic data on endangered twaite shad (Clupeidae) assessed in landlocked and anadromous populations: one or more species?

Seven Italian populations of twaite shad Alosa fallax from Northern and Central Italy were investigated to assess genetic diversity by Cytochrome b (Cytb) gene sequencing. The two ecotypes historically referred to landlocked and anadromous populations were investigated for the first time from a genetic point of view, to clarify their phylogenetic relationships. Moreover, results obtained from populations coming from separated Adriatic and Tyrrhenian basins were compared with data assessed in samples of allis shad Alosa alosa from the Atlantic basin. All the Italian samples were recognized at species level as A. fallax, differing for five mutations from A. alosa. The analyses confirmed the occurrence of a single phylogenetic lineage and of a single species within Italian waters, in both landlocked and migratory populations. The minimum spanning network identified six haplotypes for A. fallax and two haplotypes for A. alosa. The neighbour-joining tree and the maximum likelihood on the Cytb gene sequences confirmed two distinct lineages for A. alosa and A. fallax, without evidence of a separation at specific level within the A. fallax group. A weak separation due to incipient population differentiation was detected between anadromous and landlocked Italian populations, supporting the idea of a recent separation. The molecular data herein collected do not support the existence of the already controversial incipient species Alosa agone. Despite this, the two ecotypes could be considered as different management units from a conservation viewpoint.

The potential role of myostatin and neurotransmission genes in elite sport performances

Elite athletes are those who represent their sport at such major competition as the Olympic Games or World contests. The most outstanding athletes appear to emerge as a result of endogenous biologic characteristics interacting with exogenous influences of the environment, often described as a ‘Nature and Nurture’ struggle. In this work, we assessed the contribution given by 4 genes involved in muscles development (MSTN) and behavioural insights (5HTT, DAT and MAOA) to athletic performances. As for neurotransmission, 5HTT, DAT and MAOA genes have been considered as directly involved in the management of aggressiveness and anxiety.Genotypes and allelic frequencies of 5HTTLPR, MAOA-u VNTR, DAT VNTR and MSTN K153R were determined in 50 elite athletes and compared with 100 control athletes.In this work we found a significant correlation between the dopamine transporter genotype 9/9 and allele 9 and elite sport performances. On the contrary, no association was found between muscle development regulation or serotonin pathway and elite performances. Our data, for the first time, suggest a strong role of dopamine neurotransmitter in determining sport success, highlighting the role of emotional control and psycological management to reach high-level performances.