Corrigendum: One-carbon pathway metabolites are altered in the plasma of subjects with Down syndrome: relation to chromosomal dosage.

[This corrects the article DOI: 10.3389/fmed.2022.1006891.].

Performance Metrics of the Scoring System for the Diagnosis of the Beckwith-Wiedemann Spectrum (BWSp) and Its Correlation with Cancer Development.

Different scoring systems for the clinical diagnosis of the Beckwith-Wiedemann spectrum (BWSp) have been developed over time, the most recent being the international consensus score. Here we try to validate and provide data on the performance metrics of these scoring systems of the 2018 international consensus and the previous ones, relating them to BWSp features, molecular tests, and the probability of cancer development in a cohort of 831 patients. The consensus scoring system had the best performance (sensitivity 0.85 and specificity 0.43). In our cohort, the diagnostic yield of tests on blood-extracted DNA was low in patients with a low consensus score (~20% with a score = 2), and the score did not correlate with cancer development. We observed hepatoblastoma (HB) in 4.3% of patients with UPD(11)pat and Wilms tumor in 1.9% of patients with isolated lateralized overgrowth (ILO). We validated the efficacy of the currently used consensus score for BWSp clinical diagnosis. Based on our observation, a first-tier analysis of tissue-extracted DNA in patients with <4 points may be considered. We discourage the use of the consensus score value as an indicator of the probability of cancer development. Moreover, we suggest considering cancer screening for negative patients with ILO (risk ~2%) and HB screening for patients with UPD(11)pat (risk ~4%).

Down Syndrome: how to communicate the diagnosis.

Communicating the diagnosis of Down Syndrome to a couple of parents is never easy, whether before or after birth. As doctors, we must certainly rely on our own relational skills, but it is also necessary to be confident in some general indications, which are often overlooked in the strict hospital routine. This article is intended as a summary of the main articles published on this subject in the international literature, collecting and summarising the most important indications that have emerged in years of medical practice all over the world as well as in our personal experience. The diffusion of these guidelines is essential to help the doctor in this difficult task, on which there is often little training, and above all to guarantee to the parents the least traumatic communication possible.

One-carbon pathway metabolites are altered in the plasma of subjects with Down syndrome: Relation to chromosomal dosage.

Introduction: Down syndrome (DS) is the most common chromosomal disorder and it is caused by trisomy of chromosome 21 (Hsa21). Subjects with DS show a large heterogeneity of phenotypes and the most constant clinical features present are typical facies and intellectual disability (ID). Several studies demonstrated that trisomy 21 causes an alteration in the metabolic profile, involving among all the one-carbon cycle. Methods: We performed enzyme-linked immunosorbent assays (ELISAs) to identify the concentration of 5 different intermediates of the one-carbon cycle in plasma samples obtained from a total of 164 subjects with DS compared to 54 euploid subjects. We investigated: tetrahydrofolate (THF; DS n = 108, control n = 41), 5-methyltetrahydrofolate (5-methyl-THF; DS n = 140, control n = 34), 5-formyltetrahydrofolate (5-formyl-THF; DS n = 80, control n = 21), S-adenosyl-homocysteine (SAH; DS n = 94, control n = 20) and S-adenosyl-methionine (SAM; DS n = 24, control n = 15). Results: Results highlight specific alterations of THF with a median concentration ratio DS/control of 2:3, a decrease of a necessary molecule perfectly consistent with a chromosomal dosage effect. Moreover, SAM and SAH show a ratio DS/control of 1.82:1 and 3.6:1, respectively. Discussion: The relevance of these results for the biology of intelligence and its impairment in trisomy 21 is discussed, leading to the final proposal of 5-methyl-THF as the best candidate for a clinical trial aimed at restoring the dysregulation of one-carbon cycle in trisomy 21, possibly improving cognitive skills of subjects with DS.

Partial trisomy 21 with or without highly restricted Down syndrome critical region (HR-DSCR): report of two new cases and reanalysis of the genotype-phenotype association.

BACKGROUND: Down syndrome (DS) is caused by the presence of an extra copy of full or partial human chromosome 21 (Hsa21). Partial (segmental) trisomy 21 (PT21) is the duplication of only a delimited region of Hsa21 and can be associated or not to DS: the study of PT21 cases is an invaluable model for addressing genotype-phenotype correlation in DS. Previous works reported systematic reanalyses of 132 subjects with PT21 and allowed the identification of a 34-kb highly restricted DS critical region (HR-DSCR) as the minimal region whose duplication is shared by all PT21 subjects diagnosed with DS. METHODS: We report clinical data and cytogenetic analysis of two children with PT21, one with DS and the other without DS. Moreover, we performed a systematic bibliographic search for any new PT21 report. RESULTS: Clinical and cytogenetic analyses of the two PT21 children have been reported: in Case 1 the duplication involves the whole long arm of Hsa21, except for the last 2.7 Mb, which are deleted as a consequence of an isodicentric 21: the HR-DSCR is within the duplicated regions and the child is diagnosed with DS. In Case 2 the duplication involves 7.1 Mb of distal 21q22, with a deletion of 2.1 Mb of proximal 20p, as a consequence of an unbalanced translocation: the HR-DSCR is not duplicated and the child presents with psychomotor development delay but no clinical signs of DS. Furthermore, two PT21 reports recently published (named Case 3 and 4) have been discussed: Case 3 has DS diagnosis, nearly full trisomy for Hsa21 and a monosomy for the 21q22.3 region. Case 4 is a baby without DS and a 0.56-Mb duplication of 21q22.3. Genotype-phenotype correlation confirmed the presence of three copies of the HR-DSCR in all DS subjects and two copies in all non-DS individuals. CONCLUSIONS: The results presented here are fully consistent with the hypothesis that the HR-DSCR is critically associated with DS diagnosis. No exception to this pathogenetic model was found. Further studies are needed to detect genetic determinants likely located in the HR-DSCR and possibly responsible for core DS features, in particular intellectual disability.

Clinical and molecular characterization of patients affected by Beckwith-Wiedemann spectrum conceived through assisted reproduction techniques.

The prevalence of Beckwith-Wiedemann spectrum (BWSp) is tenfold increased in children conceived through assisted reproductive techniques (ART). More than 90% of ART-BWSp patients reported so far display imprinting center 2 loss-of-methylations (IC2-LoM), versus 50% of naturally conceived BWSp patients. We describe a cohort of 74 ART-BWSp patients comparing their features with a cohort of naturally conceived BWSp patients, with the ART-BWSp patients previously described in literature, and with the general population of children born from ART. We found that the distribution of UPD(11)pat was not significantly different in ART and naturally conceived patients. We observed 68.9% of IC2-LoM and 16.2% of mosaic UPD(11)pat in our ART cohort, that strongly differ from the figure reported in other cohorts so far. Since UPD(11)pat likely results from post-fertilization recombination events, our findings allows to hypothesize that more complex molecular mechanisms, besides methylation disturbances, may underlie BWSp increased risk in ART pregnancies. Moreover, comparing the clinical features of ART and non-ART BWSp patients, we found that ART-BWSp patients might have a milder phenotype. Finally, our data show a progressive increase in the prevalence of BWSp over time, paralleling that of ART usage in the last decades.

A reassessment of Jackson's checklist and identification of two Down syndrome sub-phenotypes.

Down syndrome (DS) is characterised by several clinical features including intellectual disability (ID) and craniofacial dysmorphisms. In 1976, Jackson and coll. identified a checklist of signs for clinical diagnosis of DS; the utility of these checklists in improving the accuracy of clinical diagnosis has been recently reaffirmed, but they have rarely been revised. The purpose of this work is to reassess the characteristic phenotypic signs and their frequencies in 233 DS subjects, following Jackson's checklist. 63.77% of the subjects showed more than 12 signs while none showed less than 5, confirming the effectiveness of Jackson's checklist for the clinical diagnosis of DS. An association between three phenotypic signs emerged, allowing us to distinguish two sub-phenotypes: Brachycephaly, short and broad Hands, short Neck (BHN), which is more frequent, and "non-BHN". The strong association of these signs might be interpreted in the context of the growth defects observed in DS children suggesting decreased cell proliferation. Lastly, cognitive assessments were investigated for 114 subjects. The lack of association between the presence of a physical sign or the number of signs present in a subject and cognitive skills disproves the stereotype that physical characteristics are predictive of degree of ID.

Eating and Lifestyle Habits in Youth With Down Syndrome Attending a Care Program: An Exploratory Lesson for Future Improvements.

Introduction: Children with Down Syndrome (DS) have nutritional problems with unknown implications besides increased potential for obesity. Their food habits are unknown. We aim to delineate eating and lifestyle habits of DS children attending a multispecialist program to identify the challenges they face and the potential improvements. Patients and Methods: We interacted with 34 DS children (22 males, 12 females, 2-16 years old) and their families. Food habits, medical conditions and treatments, degrees of development and physical activity, anthropometric and laboratory data were recorded over 6 months and analyzed. A 3-day food diary and a 24-h recall food frequency questionnaire were administered. Results: Twenty-nine (85%) children completed meals, only 11 (32%) received alternative food such as milk. Weaning regularly started in 25 (73%) children. Preschool children introduced adequate calories and nutrients. School children and adolescents did not reach recommendations. All age groups, as the general pediatric population, excessively ate protein and saturated fat, and preferred bread, pasta, fruit juices, meat and cold cuts. Peculiarly, pulses and fish were adequately assumed by preschool and school children, respectively. Five children (15%) were overweight/obese. Conclusions: Dietary excesses commonly found in the general pediatric population are also present in this DS group, proving a narrowing gap between the two. DS group performed better nutritionally in the early years and overweight/obesity occurrence seems contained. DS children may benefit from a practical yet professional care-program in which nutrition education may improve their growth, development and transition into adulthood.

Is the Age of Developmental Milestones a Predictor for Future Development in Down Syndrome?

Down Syndrome (DS) is the most common genetic alteration responsible for intellectual disability, which refers to deficits in both intellectual and adaptive functioning. According to this, individuals with Down Syndrome (DS) reach developmental milestones (e.g., sitting, walking, and babbling) in the same order as their typically developing peers, but later in life. Since developmental milestones are the first blocks on which development builds, the aims of the current study are to: (i) expand the knowledge of developmental milestone acquisition; and (ii) explore the relationship between developmental milestone acquisition and later development. For this purpose 105 children/adolescents with DS were involved in this study, divided in two groups, Preschoolers (n = 39) and School-age participants (n = 66). Information on the age of acquisition of Sitting, Walking, Babbling, and Sphincter Control was collected, together with cognitive, motor, and adaptive functioning. Sitting predicted later motor development, but, with age, it became less important in predicting motor development in everyday life. Babbling predicted later language development in older children. Finally, Sphincter Control emerged as the strongest predictor of motor, cognitive, language, and adaptive skills, with its role being more evident with increasing age. Our data suggest that the age of reaching the milestones considered in the study has an influence on successive development, a role that can be due to common neural substrates, the environment, and the developmental cascade effect.

The transcriptome profile of human trisomy 21 blood cells.

BACKGROUND: Trisomy 21 (T21) is a genetic alteration characterised by the presence of an extra full or partial human chromosome 21 (Hsa21) leading to Down syndrome (DS), the most common form of intellectual disability (ID). It is broadly agreed that the presence of extra genetic material in T21 gives origin to an altered expression of genes located on Hsa21 leading to DS phenotype. The aim of this study was to analyse T21 and normal control blood cell gene expression profiles obtained by total RNA sequencing (RNA-Seq). RESULTS: The results were elaborated by the TRAM (Transcriptome Mapper) software which generated a differential transcriptome map between human T21 and normal control blood cells providing the gene expression ratios for 17,867 loci. The obtained gene expression profiles were validated through real-time reverse transcription polymerase chain reaction (RT-PCR) assay and compared with previously published data. A post-analysis through transcriptome mapping allowed the identification of the segmental (regional) variation of the expression level across the whole genome (segment-based analysis of expression). Interestingly, the most over-expressed genes encode for interferon-induced proteins, two of them (MX1 and MX2 genes) mapping on Hsa21 (21q22.3). The altered expression of genes involved in mitochondrial translation and energy production also emerged, followed by the altered expression of genes encoding for the folate cycle enzyme, GART, and the folate transporter, SLC19A1. CONCLUSIONS: The alteration of these pathways might be linked and involved in the manifestation of ID in DS.

One-carbon pathway and cognitive skills in children with Down syndrome.

This work investigates the role of metabolite levels in the intellectual impairment of subjects with Down syndrome (DS). Homocysteine, folate, vitamin B12, uric acid (UA), creatinine levels and MTHFR C677T genotype were analyzed in 147 subjects with DS. For 77 subjects, metabolite levels were correlated with cognitive tests. Griffiths-III test was administered to 28 subjects (3.08-6.16 years) and WPPSI-III test was administered to 49 subjects (7.08-16.08 years). Significant correlations were found among some metabolite levels and between homocysteine levels and MTHFR C677T genotype. Moreover, homocysteine, UA and creatinine levels resulted increased with age. We did not find any correlation between metabolites and cognitive test score in the younger group. Homocysteine showed statistically significant correlation with WPPSI-III subtest scores when its level is ≥ 7.35 µmol/L, remaining correlated in higher thresholds only for non-verbal area scores. Vitamin B12 showed correlations with all WPPSI-III subtest scores when its level is < 442 pg/mL. The relevance of the present findings is the detection of a specific metabolite threshold related with a better or worse cognitive score, suggesting that vitamin B12 and homocysteine may have a role in cognitive development in children with DS.

Plasma metabolome and cognitive skills in Down syndrome.

Trisomy 21 (Down syndrome, DS) is the main human genetic cause of intellectual disability (ID). Lejeune hypothesized that DS could be considered a metabolic disease, and we found that subjects with DS have a specific plasma and urinary metabolomic profile. In this work we confirmed the alteration of mitochondrial metabolism in DS and also investigated if metabolite levels are related to cognitive aspects of DS. We analyzed the metabolomic profiles of plasma samples from 129 subjects with DS and 46 healthy control (CTRL) subjects by 1H Nuclear Magnetic Resonance (NMR). Multivariate analysis of the NMR metabolomic profiles showed a clear discrimination (up to 94% accuracy) between the two groups. The univariate analysis revealed a significant alteration in 7 metabolites out of 28 assigned unambiguously. Correlations among the metabolite levels in DS and CTRL groups were separately investigated and statistically significant relationships appeared. On the contrary, statistically significant correlations among the NMR-detectable part of DS plasma metabolome and the different intelligence quotient ranges obtained by Griffiths-III or WPPSI-III tests were not found. Even if metabolic imbalance provides a clear discrimination between DS and CTRL groups, it appears that the investigated metabolomic profiles cannot be associated with the degree of ID.

Disseminate Recurrent Folliculitis and Hidradenitis Suppurativa Are Associated Conditions: Results From a Retrospective Study of 131 Patients With Down Syndrome and a Cohort of 12,351 Pediatric Controls.

BACKGROUND: Hidradenitis suppurativa (HS) is a chronic, inflammatory, recurrent skin disease of the pilosebaceous unit characterized by protean manifestations. Several studies have found an increased incidence and earlier presentation of this disease in patients carrying trisomy 21. Patients with Down syndrome (DS) have a higher risk of developing a wide range of cutaneous manifestations, including HS and chronic folliculitis. Recently, disseminate recurrent folliculitis (DRF) has been reported as an atypical monosymptomatic feature of HS at its onset. OBJECTIVE: To assess the prevalence of HS and DRF by comparing a cohort of patients carrying trisomy 21 vs pediatric controls. METHODS: A retrospective 2-year monocentric clinical study was performed by collecting clinical data of 131 patients with DS, aged 4-36 years, followed at the Dermatology Unit and Down Syndrome Regional Center of Bologna University. Data were matched with those coming from 12,351 pediatric controls. RESULTS: In DS patients, DRF and HS showed a prevalence of, respectively, 6.8% and 24.4%, while 5.3% of patients presented both diseases. In the control group the prevalence for HS+ and DRF+ was 0.5% and 1.2%, respectively, with a 0.14% of overlap cases. The association between HS and DRF proved to be statistically significant in both groups (P < 0.05). In the DS cohort the mean age of symptoms onset was 15.67 (SD: 2.29) years for HS and 13.11 (SD: 4.93) years for DRF. Buttocks were the most frequently affected body area for DRF followed by the inguinocrural area, while in HS buttocks were less frequently involved than groins and upper thighs. CONCLUSIONS: Because of the later onset of HS, patients with DRF at an early age should be monitored for the possible onset of HS in the apocrine-bearing areas.

Prenatal diagnosis and prevalence of critical congenital heart defects: an international retrospective cohort study.

OBJECTIVES: To assess international trends and patterns of prenatal diagnosis of critical congenital heart defects (CCHDs) and their relation to total and live birth CCHD prevalence and mortality. SETTING: Fifteen birth defect surveillance programmes that participate in the International Clearinghouse for Birth Defects Surveillance and Research from 12 countries in Europe, North and South America and Asia. PARTICIPANTS: Live births, stillbirths and elective terminations of pregnancy for fetal anomaly diagnosed with 1 of 12 selected CCHD, ascertained by the 15 programmes for delivery years 2000 to 2014. RESULTS: 18 243 CCHD cases were reported among 8 847 081 births. The median total prevalence was 19.1 per 10 000 births but varied threefold between programmes from 10.1 to 31.0 per 10 000. CCHD were prenatally detected for at least 50% of the cases in one-third of the programmes. However, prenatal detection varied from 13% in Slovak Republic to 87% in some areas in France. Prenatal detection was consistently high for hypoplastic left heart syndrome (64% overall) and was lowest for total anomalous pulmonary venous return (28% overall). Surveillance programmes in countries that do not legally permit terminations of pregnancy tended to have higher live birth prevalence of CCHD. Most programmes showed an increasing trend in prenatally diagnosed CCHD cases. DISCUSSION AND CONCLUSIONS: Prenatal detection already accounts for 50% or more of CCHD detected in many programmes and is increasing. Local policies and access likely account for the wide variability of reported occurrence and prenatal diagnosis. Detection rates are high especially for CCHD that are more easily diagnosed on a standard obstetric four-chamber ultrasound or for fetuses that have extracardiac anomalies. These ongoing trends in prenatal diagnosis, potentially in combination with newborn pulse oximetry, are likely to modify the epidemiology and clinical outcomes of CCHD in the near future.

Myoclonic epilepsy with photosensitivity in infants with Pallister-Killian Syndrome.

INTRODUCTION: Pallister-Killian Syndrome (PKS) (OMIM #601803) is a rare genetic disorder caused by a mosaic tetrasomy of the short arm of chromosome 12. Epilepsy is a frequent concern in PKS patients. METHODS: we report 3 PKS patients, with early-onset myoclonic epilepsy and photosensitivity. In these children, we analysed epileptic history and the EEG phenotype. RESULTS: Epilepsy onset was in the first 2 years of life in all patients and in 2 of them myoclonic seizures were the only seizure type. In all children photosensitivity was observed and myoclonic seizures were mainly related to low-frequency (1-6 Hz) intermittent photic stimulation. Levetiracetam was effective and well tolerated in the 2 treated patients. CONCLUSIONS: early-onset myoclonic epilepsy is a possible clinical manifestation of PKS. Low-frequency photosensitivity is a peculiar bioelectrical marker in these children.

[Corrigendum] Analysis of a nanoparticle­enriched fraction of plasma reveals miRNA candidates for Down syndrome pathogenesis.

After the publication of the above paper, the authors noted that the names of a couple of the authors listed on the paper were associated with the wrong affliation: Specifically, the eighth and ninth listed authors, Francesca Antonaros and Allison Piovesan, are located at DIMES at the University of Florence (fourth affiliation address), not at CSGI, the Research Center for Colloids and Nanoscience in Florence (third affliation address). Therefore, the author and affiliation details for this paper should have been presented as follows: ALESSANDRO SALVI1, MARIKA VEZZOLI2, SARA BUSATTO1, LUCIA PAOLINI1,3, TERESA FARANDA1, EDOARDO ABENI1, MARIA CARACAUSI4, FRANCESCA ANTONAROS4, ALLISON PIOVESAN4, CHIARA LOCATELLI5, GUIDO COCCHI5,6, GUALTIERO ALVISI7, GIUSEPPINA DE PETRO1, DORIS RICOTTA1, PAOLO BERGESE1,3 and ANNALISA RADEGHIERI1,3. 1Department of Molecular and Translational Medicine, University of Brescia; 2Unit of Biostatistics, Department of Molecular and Translational Medicine, University of Brescia, I­25123 Brescia; 3CSGI, Research Center for Colloids and Nanoscience, Sesto Fiorentino, I­50019 Florence; 4Department of Experimental, Diagnostic and Specialty Medicine (DIMES), Unit of Histology, Embryology and Applied Biology, University of Bologna; 5Neonatology Unit, St. Orsola­Malpighi Polyclinic; 6Department of Medical and Surgical Sciences (DIMEC), University of Bologna, I­40138 Bologna; 7Department of Molecular Medicine, University of Padua, I­35121 Padua, Italy. The authors regret that this error with the author affiliations for Francesca Antonaros and Allison Piovesan was not noticed prior to the publication of their paper, and apologize for any inconvenience caused. [the original article was published in International Journal of Molecular Medicine 43: 2303­2318, 2018; DOI: 10.3892/ijmm.2019.4158].

Partial trisomy 21 map: Ten cases further supporting the highly restricted Down syndrome critical region (HR-DSCR) on human chromosome 21.

BACKGROUND: Down syndrome (DS) is characterized by the presence of an extra full or partial human chromosome 21 (Hsa21). An invaluable model to define genotype-phenotype correlations in DS is the study of the extremely rare cases of partial (segmental) trisomy 21 (PT21), the duplication of only a delimited region of Hsa21 associated or not to DS. A systematic retrospective reanalysis of 125 PT21 cases described up to 2015 allowed the creation of the most comprehensive PT21 map and the identification of a 34-kb highly restricted DS critical region (HR-DSCR) as the minimal region whose duplication is shared by all PT21 subjects diagnosed with DS. We reanalyzed at higher resolution three cases previously published and we accurately searched for any new PT21 reports in order to verify whether HR-DSCR limits could prospectively be confirmed and possibly refined. METHODS: Hsa21 partial duplications of three PT21 subjects were refined by adding array-based comparative genomic hybridization data. Seven newly described PT21 cases fulfilling stringent cytogenetic and clinical criteria have been incorporated into the PT21 integrated map. RESULTS: The PT21 map now integrates fine structure of Hsa21 sequence intervals of 132 subjects onto a common framework fully consistent with the presence of a duplicated HR-DSCR, on distal 21q22.13 sub-band, only in DS subjects and not in non-DS individuals. No documented exception to the HR-DSCR model was found. CONCLUSIONS: The findings presented here further support the association of the HR-DSCR with the diagnosis of DS, representing an unbiased validation of the original model. Further studies are needed to identify and characterize genetic determinants presumably located in the HR-DSCR and functionally associated to the critical manifestations of DS.

Analysis of a nanoparticle­enriched fraction of plasma reveals miRNA candidates for Down syndrome pathogenesis.

Down syndrome (DS) is caused by the presence of part or all of a third copy of chromosome 21. DS is associated with several phenotypes, including intellectual disability, congenital heart disease, childhood leukemia and immune defects. Specific microRNAs (miRNAs/miR) have been described to be associated with DS, although none of them so far have been unequivocally linked to the pathology. The present study focuses to the best of our knowledge for the first time on the miRNAs contained in nanosized RNA carriers circulating in the blood. Fractions enriched in nanosized RNA­carriers were separated from the plasma of young participants with DS and their non­trisomic siblings and miRNAs were extracted. A microarray­based analysis on a small cohort of samples led to the identification of the three most abundant miRNAs, namely miR­16­5p, miR­99b­5p and miR­144­3p. These miRNAs were then profiled for 15 pairs of DS and non­trisomic sibling couples by reverse transcription­quantitative polymerase chain reaction (RT­qPCR). Results identified a clear differential expression trend of these miRNAs in DS with respect to their non­trisomic siblings and gene ontology analysis pointed to their potential role in a number of typical DS features, including 'nervous system development', 'neuronal cell body' and certain forms of 'leukemia'. Finally, these expression levels were associated with certain typical quantitative and qualitative clinical features of DS. These results contribute to the efforts in defining the DS­associated pathogenic mechanisms and emphasize the importance of properly stratifying the miRNA fluid vehicles in order to probe biomolecules that are otherwise hidden and/or not accessible to (standard) analysis.

MTHFR C677T polymorphism analysis: A simple, effective restriction enzyme-based method improving previous protocols.

BACKGROUND: 5,10-Methylentetrahydrofolate reductase (MTHFR) C677T polymorphism is one of the most studied genetic variations in the human genome. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) is one of the most used techniques to characterize the point mutations in genomic sequences because of its suitability and low cost. The most widely used method for the MTHFR C677T polymorphism characterization was developed by Frosst et al. (1995) but appears to have some technical limitations. The aim of this study was to propose a novel PCR-RFLP method for the detection of this polymorphism. METHODS: In order to retrieve all published articles possibly describing any PCR-RFLP methods useful to analyze MTHFR C677T polymorphism, we performed systematic queries on PubMed, using a combination of Boolean operators (AND/OR) and MeSH terms. Amplify software was used in order to design a new primer pair following the optimal standard criteria. Primer-BLAST software was used to check primer pair's biological specificity. RESULTS: The analysis of previous literature showed that PCR-RFLP method remains the most used technique. None of the 108 primer pairs described was ideal with regard to main accepted primer pair biochemical technical parameters. The new primer pair amplifies a DNA-fragment of 513 base pair (bp) that, in the presence of the polymorphism, is cut by Hinf I enzyme in two pieces of 146 bp and 367 bp and clearly visible on 2% agarose gel. The level of expertise and the materials required are minimal and the protocol takes one day to carry out. CONCLUSION: Our original PCR-RFLP strategy, specifically designed to make the analysis optimal with respect to PCR primers and gel analysis, fits the ideal criteria compared to the widely used strategy by Frosst et al (1995) as well as any other PCR-RFLP strategies proposed for MTHFR C677T polymorphism genotyping to date.

Human trisomy 21 fibroblasts rescue methotrexate toxic effect after treatment with 5-methyl-tetrahydrofolate and 5-formyl-tetrahydrofolate.

Trisomy 21 causes Down syndrome (DS), the most common human genetic disorder and the leading genetic cause of intellectual disability. The alteration of one-carbon metabolism was described as the possible metabolic cause of the intellectual disability development in subjects with DS. One of the biochemical pathways involved in the one-carbon group transfer is the folate cycle. The cytotoxic drug methotrexate (MTX) is a folic acid (FA) analogue which inhibits the activity of dihydrofolate reductase enzyme involved in the one-carbon metabolic cycle. Trisomy 21 cells are more sensitive to the MTX effect than euploid cells, and in 1986 Jérôme Lejeune and Coll. demonstrated that MTX was twice as toxic in trisomy 21 lymphocytes than in control cells. In the present work, the rescue effect on MTX toxicity mediated by FA and some of its derivatives, tetrahydrofolate (THF), 5-formyl-THF, and 5-methyl-THF, in both normal and trisomy 21 skin fibroblast cells, was evaluated. A statistically significant rescue effect was obtained by 5-formyl-THF, 5-methyl-THF, and their combination, administered together with MTX. In conclusion, trisomy 21 fibroblast cell lines showed a good response to the rescue effects of 5-formyl-THF and 5-methyl-THF on the MTX toxicity almost as normal cell lines.