New microsatellite markers for Dacryodes edulis (Burseraceae), an indigenous fruit tree species from Central Africa.

Microsatellites were designed and characterized in the African fruit tree species Dacryodes edulis (Burseraceae). The fruits are commercialized throughout Central Africa and the species is present in forested environments as well as cultivated systems. The high variability of these markers makes them suitable to investigate the structure of genetic diversity in this important food tree species from Central Africa. From a genomic library obtained by next-generation sequencing, 21 new polymorphic microsatellite loci were developed. Tested on 95 individuals from four populations coming from three countries of the Congo Basin, the microsatellites displayed two to 20 alleles (mean 7.5; expected heterozygosity 0.003 to 0.937, mean 0.666). The transferability of microsatellites was effective for four other Dacryodes species (D. buettneri, D. igaganga, D. osika, D. pubescens). This set of newly developed microsatellite markers will be useful for assessing the genetic diversity and differentiation as well as gene flow patterns of D. edulis in tropical forests from Central Africa.

Myosin XI is associated with fitness and adaptation to aridity in wild pearl millet.

Phenotypic changes in plants can be observed along many environmental gradients and are determined by both environmental and genetic factors. The identification of alleles associated with phenotypic variations is a rapidly developing area of research. We studied the genetic basis of phenotypic variations in 11 populations of wild pearl millet (Pennisetum glaucum) on two North-South aridity gradients, one in Niger and one in Mali. Most of the 11 phenotypic traits assessed in a common garden experiment varied between the populations studied. Moreover, the size of the inflorescence, the number of flowers and aboveground dry mass co-varied positively with a decrease in rainfall. To decipher the genetic basis of these phenotypes, we used an association mapping strategy with a mixed model. We found two SNPs on the same myosin XI contig significantly associated with variations in the average number of flowers. Both the allele frequency of the two SNPs and the average number of flowers co-varied with the rainfall gradient on the two gradients. Interestingly, this gene was also a target of selection during domestication. The Myosin XI gene is thus a good candidate for fitness-related adaptation in wild populations.

The Arabidopsis KAKTUS gene encodes a HECT protein and controls the number of endoreduplication cycles.

In animals and plants, many cell types switch from mitotic cycles to endoreduplication cycles during differentiation. Little is known about the way in which the number of endoreduplication cycles is controlled in such endopolyploid cells. In this study we have characterized at the molecular level three mutations in the Arabidopsis gene KAKTUS ( KAK), which were previously shown specifically to repress endoreduplication in trichomes. We show that KAK is also involved in the regulation of the number of endoreduplication cycles in various organs that are devoid of trichomes. KAK encodes a protein with sequence similarity to HECT domain proteins. As this class of proteins is known to be involved in ubiquitin-mediated protein degradation, our finding suggests that the number of endoreduplication cycles that occur in several cell types is controlled by this pathway. The KAK gene defines a monophylogenetic subgroup of HECT proteins that also contain Armadillo-like repeats.

A new informative Alw 26 I polymorphism in exon 10 of the human low density lipoprotein receptor gene. Application to prenatal diagnosis. Mutations in brief no. 145. Online.

Using DNA sequencing of the coding and exon flanking regions of the low density lipoprotein receptor (LDLR) gene we identified an Alw26 I site in exon 10 by a transition G142A. The alleles are represented by one uncut fragment (A1=108bp) or two fragments (A2=82bp and 26 pb). Two other fragments (72bp and 16bp) were systematically found within the amplified product. The alleles were detected in 157 unrelated French Caucasians with A1 frequency = 0.58 and A2=0.42. The observed heterozygoty was 44.5%. Homozygous familial hypercholesterolemie (FH) has a severe clinical picture leading to death during childhood. Because it is very informative, the present polymorphism was very useful as genetic marker for clinical diagnois and counseling as we described in linkage analysis at the LDLR locus for prenatal diagnosis in a fetus who could inherit two LDLR mutant alleles from FH heterozygote parents.

High frequency of the apolipoprotein E *4 allele in African pygmies and most of the African populations in sub-Saharan Africa.

Apolipoprotein E genotypes (alleles *2, *3, and *4) have been determined in 70 Aka Pygmies and 470 unrelated African sub-Saharan subjects. Allele frequencies for Pygmies are 5.7% for APOE*2, 53.6% for APOE*3, and 40.7% for APOE*4, and the global proportions for sub-Saharan subjects are 11.6% for APOE*2, 70.6% for APOE*3, and 17.8% for APOE*4. The frequencies in some ethnic groups are statistically different from the overall mean in the Afar and the Isa, the Ewe (Togo), the Malinke (Guinea), and the Mossi; three ethnic groups have a higher allele frequency of APOE*4 (Fon, 29.4%; Zairians, 33.3%; Tutsi, 38.5%). The APOE*4 allele is considered the ancestral form because of its high frequency in African Pygmies and other aboriginal populations.

[Genotyping of apolipoprotein E (alleles epsilon 2, epsilon 3 and epsilon 4) from capillary blood]. / Génotypage de l'apolipoprotéine E (allèles epsilon 2, epsilon 3 et epsilon 4) à partir du sang capillaire.

A technique to determine epsilon 2, epsilon 3 and epsilon 4 alleles expressed at the apolipoprotein E locus (apoE genotype) is described. The proposed method is convenient for detecting this polymorphism on capillary blood spots. Capillary blood is collected on absorbent paper allowing transmission by post and prolonged conservation of samples. Even when the amount of DNA is very small, double amplification by polymerase chain reaction (PCR) from a DNA fragment comprising the two polymorphic sites enables the length of the synthetized fragment to be measured the amplification of all samples to be verified, thus avoiding false interpretations resulting from a 51-base-pair fragment due to primer self-hybridization. The digestion of this fragment by Hha I restriction enzyme and electrophoresis of the digested products give an unambiguous diagnosis of the six most frequent (epsilon 2/epsilon 2, epsilon 3/epsilon 3 epsilon 4/epsilon 4, epsilon 2/epsilon 3, epsilon 2/epsilon 4, and epsilon 3/epsilon 4). Intended for genotype screening determinations, this technique is not convenient for all rare apoE variants, which must be determined by plasma isoelectrofocusing or genomic DNA sequencing. The technique may be done performed any time, even if the subject is not fasting. It avoids the difficulties of interpretation of the isoelectrophoretic patterns induced by poor conservation of the samples or the presence of sialylated isoforms of apoE or other contaminant proteins. The modest cost of the proposed technique allows determination of the apoE genotype in large series.