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OBJECTIVE Small fiber neuropathy (SFN) is clinically and etiologically heterogeneous. Although autoimmunity has been postulated to be pathophysiologically important in SFN, few autoantibodies have been described. We aimed to identify autoantibodies associated with idiopathic SFN (iSFN) by a novel high-throughput protein microarray platform that captures autoantibodies expressed in the native conformational state. METHODS Sera from 58 SFN patients and 20 age- and gender-matched healthy controls (HCs) were screened against >1,600 immune-related antigens. Fluorescent unit readout and postassay imaging were performed, followed by composite data normalization and protein fold change (pFC) analysis. Analysis of an independent validation cohort of 33 SFN patients against the same 20 HCs was conducted to identify reproducible proteins in both cohorts. RESULTS Nine autoantibodies were screened with statistical significance and pFC criteria in both cohorts, with at least 50% change in serum levels. Three proteins showed consistently high fold changes in main and validation cohorts: MX1 (FC��=���2.99 and 3.07, respectively, p��=���0.003, q��=���0.076), DBNL (FC��=��2.11 and 2.16, respectively, p��=���0.009, q��

The National Academies of Sciences and Medicine 2020 consensus statement advocates the reinstatement of research in preconception heritable human genome editing (HHGE), despite the ethical concerns that have been voiced about interventions in the germline, and outlines criteria for its eventual clinical application to address monogenic disorders. However, the statement does not give adequate consideration to alternative technologies. Importantly, it omits comparison to fetal gene therapy (FGT), which involves gene modification applied prenatally to the developing fetus and which is better researched and less ethically contentious. While both technologies are applicable to the same monogenic diseases causing significant prenatal or early childhood morbidity, the benefits and risks of HHGE are distinct from FGT though there are important overlaps. FGT has the current advantage of a wealth of robust preclinical data, while HHGE is nascent technology and its feasibility for specific diseases still requires scientific proof. The ethical concerns surrounding each are unique and deserving of further discussion, as there are compelling arguments supporting research and eventual clinical translation of both technologies. In this Opinion, we consider HHGE and FGT through technical and ethical lenses, applying common ethical principles to provide a sense of their feasibility and acceptability. Currently, FGT is in a more advanced position for clinical translation and may be less ethically contentious than HHGE, so it deserves to be considered as an alternative therapy in further discussions on HHGE implementation.

Altering the human epigenome with gene-editing technology in attempt to treat a variety of diseases and conditions seems scientifically feasible. We explore some of the ethical and regulatory issues related to the clinical translation of human epigenetic editing arguing that such approaches should be considered akin to somatic therapies.

Objective Cluster genes, specifically the class 3 semaphorins ( SEMA3) including SEMA3C, have been associated with the development of Hirschsprung disease (HSCR) in Caucasian populations. We aimed to screen for rare and common variants in SEMA3C in Indonesian patients with HSCR. Methods In this prospective clinical study, we analyzed SEMA3C gene variants in 55 patients with HSCR through DNA sequencing and bioinformatics analyses. Results Two variants in SEMA3C were found: p.Val337Met (rs1527482) and p.Val579 = (rs2272351). The rare variant rs1527482 (A) was significantly overrepresented in our HSCR patients (9.1%) compared with South Asian controls in the 1000 Genomes (4.7%) and Exome Aggregation Consortium (ExAC; 3.5%) databases. Our analysis using bioinformatics tools predicted this variant to be evolutionarily conserved and damaging to SEMA3C protein function. Although the frequency of the other variant, rs2272351 (G), also differed significantly in Indonesian patients with HSCR (27.3%) from that in South Asian controls in 1000 Genomes (6.2%) and ExAC (4.6%), it is a synonymous variant and not likely to affect protein function. Conclusions This is the first comprehensive report of SEMA3C screening in patients of Asian ancestry with HSCR and identifies rs1527482 as a possible disease risk allele in this population.

Introduction. Variability in the motivation to approach or withdraw from others displayed in infancy is thought to have long-term effects on human social development. Frontal brain asymmetry has been linked to motivational processes in infants and adults, with greater left frontal asymmetry reflecting motivation to approach and greater right frontal asymmetry reflecting motivation to withdraw. We examined the hypothesis that variability in infants’ social motivation is linked to genetic variation in the endogenous oxytocin system. Specifically, we measured infants’ frontal brain asymmetry and later looking preferences to smiling and frowning individuals and assayed a single-nucleotide polymorphism in the CD38 gene (rs3796863) linked to autism spectrum disorder and reduced peripheral oxytocin levels. Methods. 77 11-month-old infants’ (36 female) brain responses were measured via functional near-infrared spectroscopy (fNIRS) while viewing four individuals display either smiles or frowns directed toward or away from them. This was followed by a person preference test using eyetracking. Results. Frontal brain asymmetry patterns evoked by direct-gaze faces significantly differed as a function of CD38 genotype. Specifically, while non-risk A-allele carriers displayed greater left lateralization to smiling faces (approach) and greater right lateralization to frowning faces (withdrawal), infants with the CC (ASD risk) genotype displayed withdrawal from smiling faces. During eyetracking, A-allele carriers showed a heightened preference for the individual who smiled, while CC infants preferred the individual who frowned.Conclusions. Our findings demonstrate that, from early in human ontogeny, genetic variation in the oxytocin system is linked to variability in brain and behavioral markers of social motivation.

Converging evidence suggests that oxytocin (OT) is associated with creative thinking (CT) and that release of OT depends on ADP ribosyl-cyclases (CD38 and CD157). Neural mechanisms of CT and OT show a strong association with dopaminergic (DA) pathways, yet the link between CT and CD38, CD157, dopamine receptor D2 (DRD2) and catechol-O-methyltransferase (COMT) peripheral gene expression remain inconclusive, thus limiting our understanding of the neurobiology of CT. To address this issue, two principal domains of CT, divergent thinking (AUT), were assessed. In men, both AUT is associated with gene expression of CD38, CD157, and their interaction CD38 × CD157. There were no significant associations for DA expression (DRD2, COMT, DRD2 × COMT) on both CT measures. However, analysis of the interactions of OT and DA systems reveal significant interactions for AUT in men. The full model explained a sizable 39% of the variance in females for the total CT score. The current findings suggest that OT and DA gene expression contributed significantly to cognition and CT phenotype. This provides the first empirical foundation of a more refined understanding of the molecular landscape of CT.

BACKGROUND: Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder characterized by degeneration or loss of lower motor neurons. The survival of motor neuron (SMN) 1 gene, which produces the SMN protein, has been identified as a responsible gene for the disease. SMN is ubiquitously expressed in any tissue and may play an important role on the metabolism in the human body. However, no appropriate biomarkers reflecting the alteration in the metabolism in SMA have been identified. METHODS: Low-molecular-weight metabolites were extracted from plasma of 20 human infants (9 SMA type 1 patients and 11 controls) and 9 infant mice (5 SMA-model mice, 4 control mice), and derivatized with N-methyl-N-trimethylsilyltrifluoroacetamide. Finally, the derivatized products were applied to Gas Chromatography/Mass Spectrometry apparatus. To confirm the metabolite abnormality in SMA type 1 patients, we performed SMN-silencing experiment using a hepatocyte-derived cell line (HepG2). RESULTS: We performed a comprehensive metabolomics analysis of plasma from the patients with SMA type 1 and controls, and found that phosphoethanolamine (PEA) was significantly higher in the patients than in the controls. HepG2 experiment also showed that SMN-silencing increased PEA levels. However, comprehensive metabolomics analysis of plasma from SMA-model mice and control mice showed different profile compared to human plasma; there was no increase of PEA even in the SMA-model mice plasma. CONCLUSION: Our data suggested that PEA was one of the possible biomarkers of human SMA reflecting metabolic abnormalities due to the SMN protein deficiency.

Background Spinal muscular atrophy (SMA) is a neuromuscular disease caused by homozygous deletion of SMN1 exons 7 and 8. However, exon 8 is retained in some cases, where SMN2 exon 7 recombines with SMN1 exon 8, forming a hybrid SMN gene. It remains unknown how the hybrid SMN gene contribute to the SMA phenotype. Method We analyzed 515 patients with clinical suspicion for SMA. SMN1 exons 7 and 8 deletion was detected by PCR followed by enzyme digestion. Hybrid SMN genes were further analyzed by nucleotide sequencing. SMN2 copy number was determined by real-time PCR. Results SMN1 exon 7 was deleted in 228 out of 515 patients, and SMN1 exon 8 was also deleted in 204 out of the 228 patients. The remaining 24 patients were judged to carry a hybrid SMN gene. In the patients with SMN1 exon 7 deletion, the frequency of the severe phenotype was significantly lower in the patients with hybrid SMN gene than in the patients without hybrid SMN gene. However, as for the distribution of SMN2 exon 7 copy number among the clinical phenotypes, there was no significant difference between both groups of SMA patients with or without hybrid SMN gene. Conclusion Hybrid SMN genes are not rare in Japanese SMA patients, and it appears to be associated with a less severe phenotype. The phenotype of patients with hybrid SMN gene was determined by the copy number of SMN2 exon 7, as similarly for the patients without hybrid SMN gene.

BACKGROUND: Polymerase chain reaction (PCR) analysis using DNA from dried blood spot (DBS) samples on filter paper is a critical technique for spinal muscular atrophy (SMA) newborn screening. However, DNA extraction from DBS is time-consuming, and elimination of PCR inhibitors from DBS is almost impossible. METHODS: Exon 7 of the two homologous SMA-related genes, survival motor neuron (SMN) 1 and SMN2, of five SMA patients and five controls were amplified by PCR with a punched-out circle of the DBS paper. Two types of DNA preparation methods were tested; DNA-extraction (extracted DNA was added in a PCR tube) and non-DNA-extraction (a punched-out DBS circle was placed in a PCR tube). As for the DNA polymerases, two different enzymes were compared; TaKaRa Ex Taq(™) and KOD FX Neo(™). To test the diagnostic quality of PCR products, RFLP (Restriction fragment length polymorphism) analysis with DraI digestion was performed, differentiating SMN1 and SMN2. RESULTS: In PCR using extracted DNA, sufficient amplification was achieved with TaKaRa Ex Taq(™) and KOD FX Neo(™), and there was no significant difference in amplification efficiency between them. In direct PCR with a punched-out DBS circle, sufficient amplification was achieved when KOD FX Neo(™) polymerase was used, while there was no amplification with TaKaRa Ex Taq(™). RFLP analysis of the direct PCR products with KOD FX Neo(™) clearly separated SMN1 and SMN2 sequences and proved the presence of both of SMN1 and SMN2 in controls, and only SMN2 in SMA patients, suggesting that the direct PCR products with KOD FX Neo(™) were of sufficient diagnostic quality for SMA testing. CONCLUSION: Direct PCR with DNA polymerases like KOD FX Neo(™) has potential to be widely used in SMA newborn screening in the near future as it obviates the DNA extraction process from DBS and can precisely amplify the target sequences in spite of the presence of PCR inhibitors.

BACKGROUND: Spinal Muscular Atrophy (SMA) is a common autosomal recessive disorder caused by SMN1 gene deletion. SMA has been considered an incurable disease. However, a newly-developed antisense oligonucleotide drug, nusinersen, brings about a good outcome to SMA patients in the clinical trials. Now, a screening for SMA is required for early diagnosis and early treatment so as to give a better clinical outcome to the patients. We have invented a new technology, mCOP-PCR, for SMA screening using dried blood spot (DBS) on the filter paper. One of the problems encountered in SMA screening is poor quality and quantity of DNA extracted from DBS. METHODS: DNA was extracted from DBS of six individuals. Fresh blood DNA of each individual had already been genotyped using PCR/RFLP. The fragments including the sequence of SMN1/SMN2 exon 7 were pre-amplified with conventional PCR. To determine which pre-amplified product is a better template for the real-time mCOP-PCR, we did pre-amplification with a single PCR or pre-amplification with a nested PCR. RESULTS: The real-time mCOP-PCR using pre-amplified products with a single PCR brought about ambiguous results in some SMN1-carrying individuals. However, the results of real-time mCOP-PCR following pre-amplification with a nested PCR were completely matched with those of PCR-RFLP. CONCLUSION: In our study on the real-time mCOP-PCR screening system for SMA, a nested PCR secured the DNA template quality and quantity, leading to unambiguous results of SMA screening.

BACKGROUND: Spinal Muscular Atrophy (SMA) is a common autosomal recessive neuromuscular disorder characterized by degeneration or loss of lower motor neurons. More than 95% of SMA patients show homozygous deletion for the survival motor neuron 1 (SMN1) gene. For the screening of SMN1 deletion, it is necessary to differentiate SMN1 from its highly homologous gene, SMN2. We developed a modified competitive oligonucleotide priming-PCR (mCOP-PCR) method using dried blood spot (DBS)-DNA, in which SMN1 and SMN2-specific PCR products are detected with gel-electrophoresis. Next, we added a targeted pre-amplification step prior to the mCOP-PCR step, to avoid unexpected, non-specific amplification. The pre-amplification step enabled us to combine mCOP-PCR and real-time PCR. In this study, we combined real-time mCOP-PCR and PCR-restriction fragment length polymorphism (PCR-RFLP) to develop a new screening system for detection of SMN1 deletion. METHODS: DBS samples of the subjects were stored at room temperature for a period of less than one year. Each subject had already been genotyped by the first PCR-RFLP using fresh blood DNA. SMN1/SMN2 exon 7 was collectively amplified using conventional PCR (targeted pre-amplification), the products of which were then used as a template in the real-time PCR with mCOP-primer sets. To confirm the results, the pre-amplified products were subject to the second PCR-RFLP. RESULTS: The real-time mCOP-PCR separately amplified SMN1 and SMN2 exon7, and clearly demonstrated SMN1 deletion in an SMA patient. The results of the real-time mCOP-PCR using DBS-DNA were completely consistent with those of the first and second PCR-RFLP analysis. CONCLUSION: In our new system for detection of SMN1 deletion, real-time mCOP-PCR rapidly proved the presence or absence of SMN1 and SMN2, and the results were easily tested by PCR-RFLP. This solid genotyping system will be useful for SMA screening.

BACKGROUND: Spinal Muscular Atrophy (SMA) is a common autosomal recessive neuromuscular disease characterized by defects of lower motor neurons. More than 95% of SMA patients show homozygous deletion for the survival motor neuron 1 (SMN1) gene. For the screening of SMN1 deletion using dried blood spot (DBS), we developed a new combined system with real-time “modified competitive oligonucleotide priming”-polymerase chain reaction (mCOP-PCR) and PCR restriction fragment length polymorphism (PCR-RFLP). Although our real-time mCOP-PCR method is secured enough to be gene-specific, its amplification efficiency is not as good because the reverse primers carry a nucleotide mismatched with the sequence of the pre-amplified product. The mismatch has consequently been generated in the process of introducing a restriction enzyme site in the pre-amplified products for PCR-RFLP. METHOD: DBS samples of the subjects were stored at room temperature for a period of less than one year. Each subject had already been genotyped by the first PCR-RFLP using fresh blood DNA. SMN1/SMN2 exon 7 was collectively amplified using conventional PCR (targeted pre-amplification). Pre-amplified products were used as template in the real-time mCOP-PCR, and, on the other hand, were digested with DraI enzyme (PCR-RFLP). To improve the amplification efficiency of mCOP-PCR, one nucleotide change was introduced in the original reverse primers (SMN1-COP and SMN2-COP) to eliminate the mismatched nucleotide. RESULTS: The real-time mCOP-PCR with a new primer (SMN1-COP-DRA or SMN2-COP-DRA) more rapidly and specifically amplified SMN1 and SMN2, and clearly demonstrated SMN1 deletion in an SMA patient. With the new primers, the amplification efficiencies of real-time mCOP-PCR were improved and the Cq values of SMN1 (+) and SMN2 (+) samples were significantly lowered. CONCLUSION: In the advanced version of our screening system for homozygous SMN1 deletion using DBS, the real-time mCOP-PCR with newly-designed reverse primers demonstrated the presence or absence of SMN1 and SMN2 within a shorter time, and the results were easily tested by PCR-RFLP. This rapid and accurate screening system will be useful for detection of newborn infants with SMA.

In a rapidly greying world, the notion that some individuals maintain successful aging trajectories, viz. high physical, cognitive, emotional, and social functioning in older age, is increasingly germane. Biomarkers of such successful aging are increasingly sought. Leukocyte telomere length (LTL), an emerging yardstick of cellular aging that is influenced by but distinct from chronological age, may also be associated to successful aging. Furthermore, given that socio-economic status (SES) influences successful aging trajectories, socioeconomic status may also moderate the association between chronological age and LTL. The goals of this study are to examine 1) whether successful aging is associated with LTL; 2) whether successful aging accounts for age-related LTL and 3) whether SES moderates the effect of age on LTL. Singaporean Chinese (n = 353) aged 65–80 completed a multidimensional assessment of successful aging and provided blood samples for LTL analysis. Results show that LTL negatively correlates with chronological age and positively correlates with successful aging. Successful aging mediates the association between chronological age and LTL. Moderated mediation analyses show that lower SES is associated with stronger negative associations of chronological age with successful aging and LTL. Moreover, the cognitive functioning dimension of successful aging is uniquely associated with LTL and its association with chronological age is moderated by SES. This study provides evidence that among older Singaporean Chinese with lower SES, declines in successful aging and in cognitive functioning are linked to age-related LTL shortening and hence to accelerated aging at the cellular level.

Spinal muscular atrophy (SMA) is one of the most common autosomal recessive disorders. The symptoms are caused by defects of lower motor neurons in the spinal cord. More than 95% of SMA patients are homozygous for survival motor neuron 1 (SMN1) deletion. We previously developed a screening system for SMN1 deletion based on a modified competitive oligonucleotide priming-PCR (mCOP-PCR) technique using dried blood spot (DBS) on filter paper. This system is convenient for mass screening in the large population and/or first-tier diagnostic method of the patients in the remote areas. However, this system was still time-consuming and effort-taking, because it required pre-amplification procedure to avoid non-specific amplification and gel-electrophoresis to detect the presence or absence of SMN1 deletion. When the fresh blood samples are used instead of DBS, or when the gel-electrophoresis is replaced by real-time PCR, we may have a simpler and more rapid diagnostic method for SMA.To establish a simpler and more rapid diagnostic method of SMN1 deletion using fresh blood DNA.DNA samples extracted from fresh blood and stored at 4 ℃ for 1 month. The samples were assayed using a real-time mCOP-PCR system without pre-amplification procedures. DNA samples had already been genotyped by PCR-restriction fragment length polymorphism (PCR-RFLP), showing the presence or absence of SMN1 exon 7. The DNA samples were directly subjected to the mCOP-PCR step. The amplification of mCOP-PCR was monitored in a real-time PCR apparatus.The genotyping results of the real-time mCOP-PCR system using fresh blood DNA were completely matched with those of PCR-RFLP. In this real-time mCOP-PCR system using fresh blood-DNA, it took only four hours from extraction of DNA to detection of the presence or absence of SMN1 deletion, while it took more than 12 hours in PCR-RFLP.Our real-time mCOP-PCR system using fresh blood DNA was rapid and accurate, suggesting it may be useful for the first-tier diagnostic method of SMA.

Spinal muscular atrophy (SMA) is a neuromuscular disease caused by a mutation in SMN1. SMA is classified into three subtypes (types 1, 2, 3) based on achieved motor milestones. Although NAIP and SMN2 are widely accepted as SMA-modifying factors, gender-related modifying factors or gender effects on the clinical phenotype are still controversial.A total of 122 Japanese patients with SMA, of which SMN1 was homozygously deleted, were analyzed from the perspective of the achieved motor milestone, NAIP status and SMN2 copy number.A predominance of male patients was observed in SMA type 3 (the walker group) without NAIP-deletion or with high SMN2 copy number (3 or 4 copies).We suggest the presence of gender-related modifiers on disease severity in SMA patients. The modifiers may contribute only in the presence of NAIP and a high copy number of SMN2.

Objectives The neuropeptide oxytocin regulates milk let-down during breastfeeding and maternal behavior in mammals. Oxytocin has also been shown to reduce stress through inhibitory effects on hypothalamic-pituitary-adrenal (HPA) reactivity. However, it remains unknown whether and how infant cortisol levels are affected by breastfeeding and what role the oxytocin system plays in this process. In the current study, we examined whether genetic variation in the oxytocin system impacts the cortisol response to breastfeeding in 84 mother-infant dyads. Methods Salivary cortisol was measured before and after a breastfeeding session. Mothers and infants were genotyped for a single-nucleotide polymorphism (SNP) in the CD38 gene (rs3796863). We compared between CC carriers and CA/AA carriers, as the CC genotype has been associated with reduced release of oxytocin and higher rates of autism in prior studies. Results Our results show that differences in infant and maternal cortisol responses to breastfeeding were associated with variation in maternal CD38. Specifically, CA/AA mothers displayed a significantly greater reduction in cortisol after breastfeeding than mothers with the CC genotype. Moreover, infants of CA/AA mothers showed significantly reduced cortisol levels after breastfeeding, as compared to infants of CC mothers. Conclusions The current findings demonstrate that maternal cortisol responses to breastfeeding vary as a function of their genetic capacity to release oxytocin, and this may also impact their infant’s stress regulation. This suggests a potential mechanism by which breastfeeding contributes to the development of HPA reactivity in infancy.

Spinal muscular atrophy (SMA) is a common neuromuscular disorder with autosomal recessive inheritance, resulting in the degeneration of motor neurons. The incidence of the disease has been estimated at 1 in 6000-10,000 newborns with a carrier frequency of 1 in 40-60. SMA is caused by mutations of the SMN1 gene, located on chromosome 5q13. The gene product, survival motor neuron (SMN) plays critical roles in a variety of cellular activities. SMN2, a homologue of SMN1, is retained in all SMA patients and generates low levels of SMN, but does not compensate for the mutated SMN1. Genetic analysis demonstrates the presence of homozygous deletion of SMN1 in most patients, and allows screening of heterozygous carriers in affected families. Considering high incidence of carrier frequency in SMA, population-wide newborn and carrier screening has been proposed. Although no effective treatment is currently available, some treatment strategies have already been developed based on the molecular pathophysiology of this disease. Current treatment strategies can be classified into three major groups: SMN2-targeting, SMN1-introduction, and non-SMN targeting. Here, we provide a comprehensive and up-to-date review integrating advances in molecular pathophysiology and diagnostic testing with therapeutic developments for this disease including promising candidates from recent clinical trials.

Both survival of motor neuron (SMN) genes are associated with spinal muscular atrophy; mutations in SMN1 cause the disease, and SMN2 modulates its severity. It is established that different alternative splicing of exon 7 occurs for SMN1 and SMN2, and a cryptic exon was recently found in intron 6 of both genes. Here, we characterize this cryptic exon and clarify its alternative splicing pattern in control and spinal muscular atrophy cells.

Antisense oligonucleotide (AON)-mediated exon skipping to restore dystrophin expression in Duchenne muscular dystrophy (DMD) therapy shown promise in a number of human clinical trials. Current AON design methods are semi-empirical, involving either trial-and-error and/or preliminary experimentations. Therefore, a rational approach to design efficient AONs to address the wide spectrum of patients' mutations is desirable. Retrospective studies have extracted many AON design variables, but they were not tested prospectively to design AONs for skipping DMD exons. Not only did the variables differ among the various studies, no numerical cutoff for each variable was inferred, which makes their use in AON design difficult. The challenge is to thus select a minimal set of key independent variables that can consistently design efficient AONs. In this prospective study, a novel set of design variables with respective cutoff values was used to design 23 novel AONs, each to skip one of nine DMD exons. Nineteen AONs were found to be efficacious in inducing specific exon skipping (83% of total), of which 14 were considered efficient (61% of total), i.e., they induced exon skipping in >25% of total transcripts. Notably, the satisfactory success rates were achieved by using only three design variables; namely, co-transcriptional binding accessibility of target site, presence of exonic splicing enhancers, and target length. Retrospective analyses revealed that the most efficient AON in every exon targeted has the lowest average cumulative position (ACP) score. Taking the prospective and retrospective studies together, we propose that design guidelines recommend using the ACP score to select the most efficient AON for each exon.

Patterns of Early Migration In order to gain insight into various migrations that must have happened during movement of early humans into Asia and the subsequent populating of the largest continent on Earth, the HUGO Pan-Asian SNP Consortium (p. 1541 ) analyzed genetic variation in almost 2000 individuals representing 73 Asian and two non-Asian populations. The results suggest that there may have been a single major migration of people into Asia and a subsequent south-to-north migration across the continent. While most populations from the same linguistic group tend to cluster together in terms of relatedness, several do not, clustering instead with their geographic neighbors, suggesting either substantial recent mixing among the populations or language replacement. Furthermore, data from indigenous Taiwanese populations appear to be inconsistent with the idea of a Taiwan homeland for Austronesian populations.

Retinoblastoma (Rb) is the most common intra-ocular tumor that manifests in early childhood. It is initiated by the inactivation of RB1/p105 gene, a prototype tumor suppressor gene. However, observed recurrent chromosomal aberrations accompanying RB1/p105 mutations suggest the involvement of additional mutational events. Chromosome 16q is one of the loci with recurrent losses which are likely to contain tumor suppressor genes. In this study, allelic loss was demonstrated at a second locus for retinoblastoma, RBL2/p130 on 16q12.2. Using intragenic single nucleotide polymorphisms (SNPs) (rs1074182 and rs10748) and flanking extragenic microsatellite markers (D16S411 and D16S408), 40 retinoblastoma tumor samples were analyzed. Loss of heterozygosity (LOH) of these markers was found in 11 (57.9%) out of 19 informative tumors at the RBL2/p130 gene locus and while a total of 15 (78.9%) tumors showed LOH in at least one marker. Deletions extending more than 13 cM across the pericentromeric region of 16q12.1-q13 were inferred from four tumors. Microsatellite instability was observed in two other tumors at the flanking markers. No mutations were found in RBL2/p130 exons 19-22 coding for the protein domain critical for biological activity. This is the first evidence of LOH within RBL2/p130 gene in retinoblastoma. The high frequency of allelic loss provides further evidence on the implication of this gene in retinoblastoma development and/or progression.