The polynucleotide kinase 3'-phosphatase gene (PNKP) is involved in Charcot-Marie-Tooth disease (CMT2B2) previously related to MED25.

Charcot-Marie-Tooth disease (CMT) represents a heterogeneous group of hereditary peripheral neuropathies. We previously reported a CMT locus on chromosome 19q13.3 segregating with the disease in a large Costa Rican family with axonal neuropathy and autosomal recessive pattern of inheritance (CMT2B2). We proposed a homozygous missense variant in the Mediator complex 25 (MED25) gene as causative of the disease. Nevertheless, the fact that no other CMT individuals with MED25 variants were reported to date led us to reevaluate the original family. Using exome sequencing, we now identified a homozygous nonsense variant (p.Gln517ter) in the last exon of an adjacent gene, the polynucleotide kinase 3'-phosphatase (PNKP) gene. It encodes a DNA repair protein recently associated with recessive ataxia with oculomotor apraxia type 4 (AOA4) and microcephaly, seizures, and developmental delay (MCSZ). Subsequently, five unrelated Costa Rican CMT2 subjects initially identified as being heterozygous for the same MED25 variant were found to be also compound heterozygote for PNKP. All were heterozygous for the same variant found homozygous in the large family and a second one previously associated with ataxia (p.Thr408del). Detailed clinical reassessment of the initial family and the new individuals revealed in all an adult-onset slowly progressive CMT2 associated with signs of cerebellar dysfunction such as slurred speech and oculomotor involvement, but neither microcephaly, seizures, nor developmental delay. We propose that PKNP variants are the major causative variant for the CMT2 phenotype in these individuals and that the milder clinical manifestation is due to an allelic effect.

Identification of the variant Ala335Val of MED25 as responsible for CMT2B2: molecular data, functional studies of the SH3 recognition motif and correlation between wild-type MED25 and PMP22 RNA levels in CMT1A animal models.

Charcot-Marie-Tooth (CMT) disease is a clinically and genetically heterogeneous disorder. All mendelian patterns of inheritance have been described. We identified a homozygous p.A335V mutation in the MED25 gene in an extended Costa Rican family with autosomal recessively inherited Charcot-Marie-Tooth neuropathy linked to the CMT2B2 locus in chromosome 19q13.3. MED25, also known as ARC92 and ACID1, is a subunit of the human activator-recruited cofactor (ARC), a family of large transcriptional coactivator complexes related to the yeast Mediator. MED25 was identified by virtue of functional association with the activator domains of multiple cellular and viral transcriptional activators. Its exact physiological function in transcriptional regulation remains obscure. The CMT2B2-associated missense amino acid substitution p.A335V is located in a proline-rich region with high affinity for SH3 domains of the Abelson type. The mutation causes a decrease in binding specificity leading to the recognition of a broader range of SH3 domain proteins. Furthermore, Med25 is coordinately expressed with Pmp22 gene dosage and expression in transgenic mice and rats. These results suggest a potential role of this protein in the molecular etiology of CMT2B2 and suggest a potential, more general role of MED25 in gene dosage sensitive peripheral neuropathy pathogenesis.

Late onset autosomal dominant Charcot-Marie-Tooth 2 neuropathy in a Costa Rican family.

OBJECTIVE: To describe the clinical, electrophysiologic and morphologic features of a Costa Rican family with an autosomal dominant inherited Charcot-Marie-Tooth (CMT) neuropathy. METHODS: The field study took place in Costa Rica, Central America. Seven patients underwent neurological examinations and standard electrodiagnostic tests, and a sural nerve biopsy was taken from one patient. Fifteen family members were screened for gene defects associated with CMT disease. RESULTS: Characteristic features of this family were a late age of onset (35-56 years), positive sensory symptoms and muscle cramps. Based on electrodiagnostic and morphologic data, the patients were classified as having a CMT2 neuropathy. The CMT1A duplication/HNPP deletion and point mutations in genes PMP22, MPZ, Cx32 and EGR2 implicated in the most common types of CMT disease were excluded. Subsequently, almost all known CMT loci were excluded by linkage analysis. DISCUSSION: Features of this family were a late age of onset and positive sensory symptoms. This new autosomal dominant CMT neuropathy is associated with an unknown gene defect.

Clinical and electrophysiological characteristics of autosomal recessive axonal Charcot-Marie-Tooth disease (ARCMT2B) that maps to chromosome 19q13.3.

Charcot-Marie-Tooth disease (CMT) comprises a heterogeneous group of hereditary motor and sensory peripheral neuropathies. The autosomal recessive axonal form of CMT (ARCMT2) is rare. Eight patients of a large consanguineous family of Spanish ancestry in Costa Rica were diagnosed with ARCMT2B; previous genetic studies of this family revealed linkage to chromosome 19q13.3. The clinical and electrophysiological features of these patients are reported. All patients presented with a symmetric motor and sensory neuropathy, which was more pronounced in the lower limbs. Further, distal muscle wasting and impaired deep tendon reflexes were found. Age at onset was between 26 and 42 years, and the disease duration ranged from 2 to 19 years. Electrophysiological studies revealed a primary axonal degenerative process. The clinical characteristics of this family differed in several aspects from previously reported families with ARCMT2.

Is the Central Valley of Costa Rica a genetic isolate?

In the last decade, the Costa Rican Central Valley population (CRCV), has received considerable scientific attention, attributed in part to a particularly interesting population structure. Two different and contradictory explanations have emerged: (1) An European-Amerindian-African admixed population, with some regional genetic heterocigosity and moderate degrees of consanguinity, similar to other Latin-American populations. (2) A genetic isolate, with a recent founder effect of European origin, genetically homogeneous, with a high intermarriage rate, and with a high degree of consanguinity. Extensive civil and religious documentation, since the settlement of the current population, allows wide genealogy and isonymy studies useful in the analysis of both hypotheses. This paper reviews temporal and spatial aspects of endogamy and consanguinity in the CRCV as a key to understand population history. The average inbreeding coefficients (a) between 1860 and 1969 show a general decrease within time. The consanguinity in the CRCV population is not homogeneous, and it is related to a variable geographic pattern. Results indicate that the endogamy frequencies are high but in general it was not correlated with a values. The general tendency shows a consanguinity decrease in time, and from rural to urban communities, repeating the tendencies observed in other countries with the same degree of development, and follows the general Western World tendency. Few human areas or communities in the world can be considered true genetic isolates. As shown, during last century, the CRCV population has had consanguinity values that definitively do not match those of true genetic isolates. A clear knowledge of the Costa Rican population genetic structure is needed to explain the origin of genetic diseases and its implications to the health system.

[Which are the most influential journals, books and scientists in Latin American biology?]. / Cuáles son las revistas, libros y personas más influyentes en la biología latinoamericana?

A survey was distributed by e-mail to 553 biologists who study the Neotropics, in order to identify the journals, books and researchers with the greatest influence over Latin American biology. The biologists' database of the Revista de Biología Tropical was used to obtain their addresses. One third of them answered. The Revista de Biología Tropical is considered the most influential journal in the region. The majority of other influential journals are published in developed countries. The thematic distribution of answers, as well as independent assessments found in the literature, indicate that these and other survey results are not biased by the use of the journal's database. By subject, marine and ecological journals are the most influential. In contrast with American science, there are no researchers or books that clearly dominate the field. These results hint to the subjectivity of many awards and qualifications and possibly reflect a lack of tradition regarding appearance of local scientists in the mass media, the small capacity of world wide diffusion for local research and the low priority of science in the Iberoamerican culture. Latin American journals should improve, specially through efficient communication with authors, stringent rejection of inferior manuscripts and through widespread and timely distribution. The marked dominance by male researchers may reflect the lower number of women in the field, and social inequality. Despite the absence of "superstars", there was a correlation: most scientists in the "list of outstanding researchers" were from large countries. The publication of the most influential journal in one of the smallest countries of the region might reflect the relatively long period of existence of the Revista (half a century), the lack of other alternatives in the region and the journal's inclusion in international indices. Recommendations for Latin American science include a selection of the best journals to receive financial support and the establishment, with help from the mass media, of a group of selected researchers as role models for the new generations.

Genotype profiles for the Costa Rican population at 7 PCR-based loci.

Complete electronic DNA profiles of 2006 randomly selected Costa Ricans, typed for 7 PCR-based loci, are presented. Such data may prove valuable for anthropological and forensic studies of the Costa Rican population.

Is the Central Valley of Costa Rica a genetic isolate?: [review]

In the last decade, the Costa Rican Central Valley population (CRCV), has received considerable scientific attention, attributed in part to a particularly interesting population structure. Two different and contradictory explanations have emerged: (1) An European-Amerindian-African admixed population, with some regional genetic heterocigosity and moderate degrees of consanguinity, similar to other Latin-American populations. (2) A genetic isolate, with a recent founder effect of European origin, genetically homogeneous, with a high intermarriage rate, and with a high degree of consanguinity. Extensive civil and religious documentation, since the settlement of the current population, allows wide genealogy and isonymy studies useful in the analysis of both hypotheses. This paper reviews temporal and spatial aspects of endogamy and consanguinity in the CRCV as a key to understand population history. The average inbreeding coefficients (a) between 1860 and 1969 show a general decrease within time. The consanguinity in the CRCV population is not homogeneous, and it is related to a variable geographic pattern. Results indicate that the endogamy frequencies are high but in general it was not correlated with a values. The general tendency shows a consanguinity decrease in time, and from rural to urban communities, repeating the tendencies observed in other countries with the same degree of development, and follows the general Western World tendency. Few human areas or communities in the world can be considered true genetic isolates. As shown, during last century, the CRCV population has had consanguinity values that definitively do not match those of true genetic isolates. A clear knowledge of the Costa Rican population genetic structure is needed to explain the origin of genetic diseases and its implications to the health system.

La implementación forense de la tecnología del ADN en Costa Rica: un análisis retrospectivo: [revisión] / Forensic implementation of DNA technology in Costa Rica: a retrospective analysis: [review]

La reciente utilización de la tecnología del ADN para la identificación individual a traído consigo una revolución en las ciencias forenses, que ha alcanzado también a la America Latina. El análisis histórico muestra que en Costa Rica sehan logrado importantes avances y en la actualidad se encuentra consolidado el trabajo con los STRs, y se están en proceso de implementación los marcadores de ADNmt y del cromosoma Y. Sin embargo, la incorporación delas innovaciones de la genética forense se ha venido realizando, cíclicamente, de 5 a 10 años tarde respecto a lospaises desarrollados en este campo. Se espera un cambio de actitud en el futuro, al estar disponibles nuevas generacionesde marcadores de ADN, que permitan explotar a corto plazo todo el potencial de esta útil herramienta al servicio de la justicia.

Genotype profiles for the Costa Rican population at 7 PCR-based loci

Complete electronic DNA profiles of 2006 randomly selected Costa Ricans, typed for 7 PCR-based loci, are presented. Such data may prove valuable for anthropological and forensic studies of the Costa Rican population.

Análisis de varios marcadores genéticos clásicos en la población de Costa Rica / Analysis of various classical genetic markers in the Costa Rica population

A study of several loci blood groups (ABO, Diego, Duffy, Kell, Kidd, Lewis, Lutheran, MNSs, P, Rhesus and Secretor), and Hp serum protein was carried out on a sample of 2,196 unrelated Costa Rican individuals of both sexes. Data was classified and analyzed according to geographic regions. Gene frequencies and the goodness of fit to Hardy-Weinberg equilibrium were estimated by the maximum likelihood method. A geographic structuring was observed in the Costa Rican population. All the regions of Costa Rica show higher heterozigosity values than the ones observed in the indigenous Costa Rican groups, but similar or slightly higher than the ones observed in the Spanish populations. The genetic distance analysis evidenced that the regions of Costa Rica group close to each other in intermediate positions between the Amerindians and the Spanish, fact that is coherent with the statement that attributes a intermediate origin to the general population of Costa Rica. The data contradicts the idea that the Central region has a radically different population than the rest of the country. The outcome of these markers revealed poor values of exclusion probability in forensic and paternity cases, which confirms the importance of their replacement for DNA markers in the outlines of human identification of judicial investigation systems. These results are similar to other studies made in Latin American populations.

Nicaraguan population data on LDLR, GYPA, D7S8, HBGG, GC and HLA-DQA1 loci

Nicaraguans have become the most numerous and fastest increasing minority in Costa Rica: at present they represent around 6 of the total population of the country. We have analyzed the allele and genotype frequencies of six PCR-based genetic markers (LDLR, GYPA, HBGG, D7S8, GC, and HLA-DQA1) in 100 unrelated Nicaraguans living in Costa Rica. All loci studied were in Hardy-Weinberg equilibrium. Some statistical parameters of forensic interest were also calculated (h, PD and CE). Allele frequencies of the markers HLA-DQA1 and GYPA were found to be significantly different between the populations of Nicaragua and Costa Rica. Nevertheless, genetic distances showed that Nicaragua is close to other Hispanic-admixed populations like those from Argentina, Chile, Colombia, Costa Rica, and USA Hispanics. The loci set was assessed to be useful for paternity testing and individual identification in the Nicaraguan population residing in Costa Rica.