Rapid prenatal diagnosis of trisomy 21 by real-time quantitative polymerase chain reaction with amplification of small tandem repeats and S100B in chromosome 21

A Review of Biomarkers of Amyotrophic Lateral Sclerosis: A Pathophysiologic Approach

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive degeneration of upper and lower motor neurons. The heterogeneous nature of ALS at the clinical, genetic, and pathological levels makes it challenging to develop diagnostic and prognostic tools that fit all disease phenotypes. Limitations associated with the functional scales and the qualitative nature of mainstay electrophysiological testing prompt the investigation of more objective quantitative assessment. Biofluid biomarkers have the potential to fill that gap by providing evidence of a disease process potentially early in the disease, its progression, and its response to therapy. In contrast to other neurodegenerative diseases, no biomarker has yet been validated in clinical use for ALS. Several fluid biomarkers have been investigated in clinical studies in ALS. Biofluid biomarkers reflect the different pathophysiological processes, from protein aggregation to muscle denervation. This review takes a pathophysiologic approach to summarizing the findings of clinical studies utilizing quantitative biofluid biomarkers in ALS, discusses the utility and shortcomings of each biomarker, and highlights the superiority of neurofilaments as biomarkers of neurodegeneration over other candidate biomarkers.

Aberrant astrocyte protein secretion contributes to altered neuronal development in multiple models of neurodevelopmental disorders

Astrocytes negatively impact neuronal development in many models of neurodevelopmental disorders (NDs); however, how they do this, and if mechanisms are shared across disorders, is not known. In this study, we developed a cell culture system to ask how astrocyte protein secretion and gene expression change in three mouse models of genetic NDs (Rett, Fragile X and Down syndromes). ND astrocytes increase release of Igfbp2, a secreted inhibitor of insulin-like growth factor (IGF). IGF rescues neuronal deficits in many NDs, and we found that blocking Igfbp2 partially rescues inhibitory effects of Rett syndrome astrocytes, suggesting that increased astrocyte Igfbp2 contributes to decreased IGF signaling in NDs. We identified that increased BMP signaling is upstream of protein secretion changes, including Igfbp2, and blocking BMP signaling in Fragile X and Rett syndrome astrocytes reverses inhibitory effects on neurite outgrowth. This work provides a resource of astrocyte-secreted proteins in health and ND models and identifies novel targets for intervention in diverse NDs.

Circulating nucleic acids in plasma and serum: applications in diagnostic techniques for noninvasive prenatal diagnosis

The analysis of fetal nucleic acids in maternal blood 13 years ago has led to the initiation of noninvasive methods for the early determination of fetal gender, rhesus D status, and a number of aneuploid disorders and hemoglobinopathies. Subsequently, a comparatively large quantity of fetal DNA and RNA has been demonstrated in amniotic fluid as well as small amounts in premature infant saliva. The DNA and RNA in amniotic fluid has permitted an analysis of core transcriptomes, whilst the DNA and RNA in saliva allows the early detection and treatment monitoring of fetal developmental problems. These aspects are discussed together with the methodology and limits of analysis for noninvasive prenatal diagnosis in predictive, preventive, and personalized medicine.

A novel de novo missense mutation in TP63 underlying germline mosaicism in AEC syndrome: implications for recurrence risk and prenatal diagnosis

Ankyloblepharon-ectodermal defects-cleft lip/palate (AEC) syndrome is a rare autosomal dominant ectodermal dysplasia syndrome. It is caused by heterozygous mutations in TP63, encoding a transcriptional factor of the p53 family. Mutations in TP63, mainly missense in exons 13 and 14 encoding the sterile alpha motif (SAM) and the transactivation inhibitory (TI) domains, account for 99% of mutations in individuals with AEC syndrome. Of these, ≥70% are de novo mutations, present in the affected patient, but not in parents nor in healthy siblings. However, when a mutation appears de novo, it is not possible to differentiate between a sporadic mutation, or germline mosaicism in the parents. In this latter case, there is a risk of having additional affected offspring. We describe two sisters with AEC syndrome, whose parents were unaffected. Both patients carried the heterozygous c.1568T>C substitution in exon 13 of TP63, resulting in a p.L523P change in the SAM domain of the protein. Analyses of DNA from parental blood cells, seminal fluid (from the father) and maternal cells (buccal, vaginal, and cervical) did not reveal the mutation, suggesting that the mosaicism may involve a very low percentage of cells (very low grade somatic mosaicism) or, more likely, maternal gonadal mosaicism. Mosaicism must be considered for the assessment of recurrence risk during genetic counseling in AEC syndrome, and pre-implantation/prenatal genetic diagnosis should be offered to all couples, even when the mutation is apparently de novo.

Determination of sensitivity and specificity of a novel gene dosage assay for prenatal screening of trisomy 21 syndrome

OBJECTIVE

To compare the gene dosage results achieved by a novel multiplex quantitative assay with cytogenetic and quantitative fluorescent polymerase chain reaction (QF-PCR) analysis for prenatal screening of trisomy 21 syndrome on corresponding fetal samples.

DESIGN AND METHODS

Fetal samples (n=134) were collected from pregnant women considered high risk for having trisomy 21 affected fetus. Cytogenetic analysis and QF-PCR were performed. Then, the relative gene dosage of DSCAM and DYRK1A2 genes was determined on corresponding samples using comparative delta cycle of threshold (ΔC(T)) method.

RESULTS

The mean gene dosage ratio was 1.55 ± 0.11 (95% CI:1.51-1.58) in trisomy 21 cases and 1.01 ± 0.12 (95% CI:0.98-1.03) in normal samples (p value<0.001). The results were in agreement to the results of cytogenetic and QF-PCR analysis with the overall specificity of 0.96 (95% CI:0.91-0.98) and the sensitivity of 0.80 (95% CI:0.49-0.94).

CONCLUSIONS

This gene dosage assay is appropriate for the screening of high risk pregnant women and is readily amenable to automation.

Effects of S100B on Serotonergic Plasticity and Neuroinflammation in the Hippocampus in Down Syndrome and Alzheimer's Disease: Studies in an S100B Overexpressing Mouse Model

S100B promotes development and maturation in the mammalian brain. However, prolonged or extensive exposure can lead to neurodegeneration. Two important functions of S100B in this regard, are its role in the development and plasticity of the serotonergic neurotransmitter system, and its role in the cascade of glial changes associated with neuroinflammation. Both of these processes are therefore accelerated towards degeneration in disease processes wherein S100B is increased, notably, Alzheimer's disease (AD) and Down syndrome (DS). In order to study the role of S100B in this context, we have examined S100B overexpressing transgenic mice. Similar to AD and DS, the transgenic animals show a profound change in serotonin innervation. By 28 weeks of age, there is a significant loss of terminals in the hippocampus. Similarly, the transgenic animals show neuroinflammatory changes analogous with AD and DS. These include decreased numbers of mature, stable astroglial cells, increased numbers of activated microglial cells and increased microglial expression of the cell surface receptor RAGE. Eventually, the S100B transgenic animals show neurodegeneration and the appearance of hyperphosphorylated tau structures, as seen in late stage DS and AD. The role of S100B in these conditions is discussed.

Neonatal S100B protein levels after prenatal exposure to selective serotonin reuptake inhibitors

OBJECTIVE

This study investigated neonatal S100B levels as a biomarker of prenatal selective serotonin reuptake inhibitor (SSRI) exposure.

METHODS

Maternal (delivery; N = 53) and neonatal (cord; N = 52) serum S100B levels were compared between prenatally SSRI-exposed (maternal, N = 36; neonatal, N = 37; duration: 230 +/- 71 days) and nonexposed (maternal, N = 17; neonatal, N = 15) groups. Measures of maternal depression and anxiety symptoms were assessed during the third trimester (33-36 weeks), and neonatal outcomes, including Apgar scores, birth weight, gestational age at birth, and symptoms of poor neonatal adaptation, were recorded.

RESULTS

S100B levels were significantly lower in prenatally SSRI-exposed neonates than in nonexposed neonates, controlling for gestational age and third-trimester maternal mood (P = .036). In contrast, SSRI-exposed mothers had significantly higher maternal serum S100B levels, compared with nonexposed mothers (P = .014), even controlling for maternal mood in the third trimester. S100B levels were not associated with maternal or neonatal drug levels, duration of prenatal exposure, demographic variables, or risk for poor neonatal adaptation.

CONCLUSIONS

Prenatal SSRI exposure was associated with decreased neonatal serum S100B levels, controlling for prenatal maternal mood. Neonatal S100B levels did not reflect neonatal behavioral outcomes and were not related to pharmacologic indices. These findings are consistent with prenatal alcohol and cocaine exposures, which also alter central serotonin levels.

S100B in neuropathologic states: the CRP of the brain?

In recent years there has been a proliferation of interest in the brain-specific protein S100B, its many physiologic roles, and its behaviour in various neuropathologic conditions. Since the mid-1960s, its wide variety of intracellular and extracellular activities has been elucidated, and it has also been implicated in an increasing number of central nervous system (CNS) disorders. S100B is part of a superfamily of proteins, some of which (including S100B) have been implicated as calcium-dependent regulatory proteins that modulate the activity of effector proteins or cells. S100B is primarily an astrocytic protein. Within cells, it may have a role in signal transduction, and it is involved in calcium homeostasis. Information about the functional implication of S100B secretion by astrocytes into the extracellular space is scant but there is substantial evidence that secreted glial S100B exerts trophic or toxic effects depending on its concentration. This review summarises the historic development and current knowledge of S100B, including recent interesting findings relating S100B to a diversity of CNS pathologies such as traumatic brain injury, Alzheimer's disease, Down's syndrome, schizophrenia, and Tourette's syndrome. These broad implications have led some workers to describe S100B as 'the CRP (C-reactive protein) of the brain.' This review also examines S100B's potential role as a neurologic screening tool, or biomarker of CNS injury, analogous to the role of CRP as a marker of systemic inflammation.

Practical application of fluorescent quantitative PCR on Trisomy 21 in Chinese Han population

OBJECTIVE

To apply the fluorescent quantitative PCR method on the detection of Trisomy 21 by D21S11 locus and make a foundation for rapid prenatal diagnosis of Trisomy 21.

METHODS

About 409 controls (39 amniotic fluid samples and 370 peripheral blood samples) and 35 patients (4 amniotic fluid samples and 31 peripheral blood samples) with Trisomy 21 were tested using fluorescent quantitative PCR by amplification of DNA fragment on D21S11 STR locus. The results were compared with conventional cytogenetic analysis to confirm the utility of this method. And the allele frequency distributions of D21S11 STR locus were analyzed.

RESULTS

The 95% reference interval of fluorescent intensity ratios of peak heights of PCR products amplified from two alleles on D21S11 locus ranged from 0.84 to 1.42 (1.13 +/- 0.29) in heterozygous controls. About 19 out of 35 patients showed a "diallelic" pattern and their height ratio of fluorescent peaks of PCR products amplified from two alleles in patients with "diallelic" patterns were all outside of the 95% reference range of controls. The PCR products of DNA from 12 patients presented the third allele. No sample with the "monoallelic" pattern was found. Four chimeras diagnosed by cytogenetic method could not be diagnosed by this method. There were 17 and 11 alleles found in controls and patients, respectively. About 343 out of 409 controls were heterozygous and the heterozygosity was 83.86%. We did not find any significant differences in the frequency distributions of alleles on D21S11 locus between controls and patients. But there were significant differences in the frequency distributions of alleles on D21S11 locus between controls and patients. But there were significant differences in the frequency distributions of alleles on D21S11 locus among different populations.

CONCLUSIONS

The fluorescent quantitative polymerase chain reaction method was rapid, accurate, and only small amount of starting material was needed, it could be applied in rapid prenatal diagnosis of Trisomy 21. D21S11 was a good marker with high heterozygosity for the screening of Trisomy 21. And the frequency distributions of alleles on D21S11 locus were significantly related to ethnic background.