The role of cryptotephra in refining the chronology of Late Pleistocene human evolution and cultural change in North Africa

© 2014.Sites in North Africa hold key information for dating the presence of Homo sapiens and the distribution of Middle Stone Age (MSA), Middle Palaeolithic (MP) and Later Stone Age (LSA) cultural activity in the Late Pleistocene. Here we present new and review recently published tephrochronological evidence for five cave sites in North Africa with long MSA/MP and LSA cultural sequences. Four tephra horizons have been identified at the Haua Fteah (Cyrenaica, Libya). They include cryptotephra evidence for the Campanian Ignimbrite (CI) eruption dating to ~39 ka that allows correlation with other Palaeolithic sequences in the eastern Mediterranean and as far north as Russia. Cryptotephra have also been recorded from the Moroccan sites of Taforalt, Rhafas and Dar es-Soltane 1. At Taforalt the geochemical composition suggests a provenance in the Azores, while examples from Sodmein (Egypt) appear to derive from central Anatolia and another unknown source. In these latter examples chemical compositional data from relevant proximal volcanic centres is currently lacking so the identification of tephra in layers of known age and cultural association provides the first reliable age determinations for distal volcanic events and their geographical extent. The future potential for tephrochronological research in North Africa is also discussed

Artificial oocyte activation with calcium ionophore does not cause a widespread increase in chromosome segregation errors in the second meiotic division of the oocyte

Objective: To study the effect of artificial oocyte activation (AOA) on chromosome segregation errors in the meiotic divisions. Design: Prospective cohort study with historical control. Setting: Private/academic IVF centers. Patient(s): Fifty-six metaphase II oocytes were donated from 12 patients who had undergone IVF between June 2008 and May 2009. Intervention(s): Oocytes were activated by 40 minutes' exposure to 100 μM calcium-ionophore. The activated oocyte was tubed and analyzed by array comparative genomic hybridization and/or single-nucleotide polymorphism genotyping and maternal haplotyping (meiomapping). A control sample of embryos derived from normally fertilized oocytes was included for comparison. Main outcome measure(s): Incidence of chromosome segregation errors in artificially activated and normally fertilized oocytes in relation to pronuclear evaluation. Result(s): Of 49 oocytes that survived the warming procedure, thirty-nine (79.6%) activated. Most activated normally, resulting in extrusion of the second polar body and formation of a single or no pronucleus (2PB1PN: 30 of 39, 76.9%; or 2PB0PN: 5 of 39, 12.8%). Twenty-seven of these were analyzed, and 16 (59.3%) were euploid, showing no effect of AOA on meiotic segregation. Single-nucleotide polymorphism analysis of normally activated oocytes confirmed normal segregation of maternal chromosomes. No difference in the proportion of meiosis II type errors was observed between artificially activated oocytes (28.6%; 95% confidence interval 3.7%-71.0%) compared with embryos obtained from normally fertilized oocytes (44.4%; 95% confidence interval 13.7%-78.8%). The abnormally activated oocytes, with ≥2PN (4 of 39, 10.3%) were diploid, indicating a failure to coordinate telophase of meiosis II with polar body extrusion. Conclusion(s): From this preliminary dataset, there is no evidence that AOA causes a widespread increase in chromosome segregation errors in meiosis II. However, we recommend that it be applied selectively to patients with specific indications

Live birth after PGD with confirmation by a comprehensive approach (karyomapping) for simultaneous detection of monogenic and chromosomal disorders.

Preimplantation genetic diagnosis (PGD) for monogenic disorders has the drawback of time and cost associated with tailoring a specific test for each couple, disorder, or both. The inability of any single assay to detect the monogenic disorder in question and simultaneously the chromosomal complement of the embryo also limits its application as separate tests may need to be carried out on the amplified material. The first clinical use of a novel approach ('karyomapping') was designed to circumvent this problem. In this example, karyomapping was used to confirm the results of an existing PGD case detecting both chromosomal abnormalities and a monogenic disorder (Smith-Lemli-Opitz [SLO] syndrome) simultaneously. The family underwent IVF, ICSI and PGD, and both polar body and cleavage stage biopsy were carried out. Following whole genome amplification, array comparative genomic hybridisation of the polar bodies and minisequencing and STR analysis of single blastomeres were used to diagnose maternal aneuploidies and SLO status, respectively. This was confirmed, by karyomapping. Unlike standard PGD, karyomapping required no a-priori test development. A singleton pregnancy and live birth, unaffected with SLO syndrome and with no chromosome abnormality, ensued. Karyomapping is potentially capable of detecting a wide spectrum of monogenic and chromosome disorders and, in this context, can be considered a comprehensive approach to PGD