Metopic suture and RUNX2, a key transcription factor in osseous morphogenesis with possible important implications for human brain evolution.

BACKGROUND: Overall, the comparative data available on the timing of metopic suture closure in present-day and fossil members of human lineage, as well as great apes, seem to indicate that human brain evolution occurred within a complex network of fetopelvic constraints, which required modification of frontal neurocranial ossification patterns, involving delayed fusion of the metopic suture. It is very interesting that the recent sequencing of the Neanderthal genome has revealed signs of positive selection in the modern human variant of the RUNX2 gene, which is known to affect metopic suture fusion in addition to being essential for osteoblast development and proper bone formation. It is possible that an evolutionary change in RUNX2, affecting aspects of the morphology of the upper body and cranium, was of importance in the origin of modern humans. Thus, to contribute to a better understanding of the molecular evolution of this gene probably implicated in human evolution, we performed a comparative bioinformatic analysis of the coding sequences of RUNX2 in Homo sapiens and other non-human Primates. RESULTS: We found amino-acid sequence differences between RUNX2 protein isoforms of Homo sapiens and the other Primates examined, that might have important implications for the timing of metopic suture closure. CONCLUSIONS: Further studies are needed to clear the potential distinct developmental roles of different species-specific RUNX2 N-terminal isoforms. Meantime, our bioinformatic analysis, regarding expression of the RUNX2 gene in Homo sapiens and other non-human Primates, has provided a contribution to this important issue of human evolution.

Transcranial sonography: a technique for the study of the temporal lobes of the human and non-human primate brain.

We developed a modified transcranial sonography technique to study the morphology of the temporal lobe, a brain region involved in language, memory and social functions in humans that can be visualized in correspondence of the acoustic window of the temporal squama. Previous studies raise the possibility that a unique derived feature of Homo sapiens is a relatively larger temporal lobe compared to those of other hominins and apes. Such a brain reorganization might have contributed to the evolution of various "higher" cognitive functions of Homo sapiens, including language. Hence, the importance of further comparative analyses of the temporal region. With the technique that we developed we were able to study the meninges, the subarachnoidal space and the cortex of the human temporal lobe. The spatial resolution and the ability to visualize structures of 200-300 microm size led us to hypothesize that the linear structures parallel to the subarachnoidal space might be referred to the neuronal layers of the cortex. The low cost, simplicity and safety of the procedure suggest that this technique may have a significant potential in the comparative study of the primate temporal lobe. Furthermore, the procedure described here can also be used for the study of vascularization of the meninges, in order to better understand the evolutionary relationships between the neurocranial shape and the middle meningeal vessels in living and fossil human species.

Volatile signals during pregnancy: a possible chemical basis for mother-infant recognition.

Human pheromones play a role in regulating relationships and apparently influence partner choice and mother-infant recognition. We analyzed the chemical content of volatiles from sweat patch samples from the para-axillary and nipple-areola regions of women during pregnancy and after childbirth. Solid phase microextraction was used to extract the volatile compounds, which were then characterized and quantified by gas chromatography-mass spectrometry. During pregnancy, women developed a distinctive pattern of five volatile compounds common to the para-axillary and nipple-areola regions (1-dodecanol, 1-1'-oxybis octane, isocurcumenol, alpha-hexyl-cinnamic aldehyde, and isopropyl myristate). These compounds were absent outside pregnancy and had slightly different patterns in samples from the two body areas. Differentiation of the volatile patterns among pregnant women may help newborns to distinguish their own mothers.

Genetic analysis of the skeletal remains attributed to Francesco Petrarca.

We report on the mitochondrial DNA (mtDNA) analysis of the supposed remains of Francesco Petrarca exhumed in November 2003, from the S. Maria Assunta church, in Arquà Padua (Italy) where he died in 1374. The optimal preservation of the remains allowed the retrieval of sufficient mtDNA for genetic analysis. DNA was extracted from a rib and a tooth and mtDNA sequences were determined in multiple clones using the strictest criteria currently available for validation of ancient DNA sequences, including independent replication. MtDNA sequences from the tooth and rib were not identical, suggesting that they belonged to different individuals. Indeed, molecular gender determination showed that the postcranial remains belonged to a male while the skull belonged to a female. Historical records indicated that the remains were violated in 1630, possibly by thieves. These results are consistent with morphological investigations and confirm the importance of integrating molecular and morphological approaches in investigating historical remains.

The Etruscans: a population-genetic study.

The origins of the Etruscans, a non-Indo-European population of preclassical Italy, are unclear. There is broad agreement that their culture developed locally, but the Etruscans' evolutionary and migrational relationships are largely unknown. In this study, we determined mitochondrial DNA sequences in multiple clones derived from bone samples of 80 Etruscans who lived between the 7th and the 3rd centuries b.c. In the first phase of the study, we eliminated all specimens for which any of nine tests for validation of ancient DNA data raised the suspicion that either degradation or contamination by modern DNA might have occurred. On the basis of data from the remaining 30 individuals, the Etruscans appeared as genetically variable as modern populations. No significant heterogeneity emerged among archaeological sites or time periods, suggesting that different Etruscan communities shared not only a culture but also a mitochondrial gene pool. Genetic distances and sequence comparisons show closer evolutionary relationships with the eastern Mediterranean shores for the Etruscans than for modern Italian populations. All mitochondrial lineages observed among the Etruscans appear typically European or West Asian, but only a few haplotypes were found to have an exact match in a modern mitochondrial database, raising new questions about the Etruscans' fate after their assimilation into the Roman state.

Evidence for a genetic discontinuity between Neandertals and 24,000-year-old anatomically modern Europeans.

During the late Pleistocene, early anatomically modern humans coexisted in Europe with the anatomically archaic Neandertals for some thousand years. Under the recent variants of the multiregional model of human evolution, modern and archaic forms were different but related populations within a single evolving species, and both have contributed to the gene pool of current humans. Conversely, the Out-of-Africa model considers the transition between Neandertals and anatomically modern humans as the result of a demographic replacement, and hence it predicts a genetic discontinuity between them. Following the most stringent current standards for validation of ancient DNA sequences, we typed the mtDNA hypervariable region I of two anatomically modern Homo sapiens sapiens individuals of the Cro-Magnon type dated at about 23 and 25 thousand years ago. Here we show that the mtDNAs of these individuals fall well within the range of variation of today's humans, but differ sharply from the available sequences of the chronologically closer Neandertals. This discontinuity is difficult to reconcile with the hypothesis that both Neandertals and early anatomically modern humans contributed to the current European gene pool.

Ancient DNA analysis of the delta F508 mutation.

When working with highly degraded DNA, validating the results of a slightly polymorphic system always complicates the analysis because of the difficulties in recognizing contamination and artifacts. Recognition can be greatly simplified by employing a multiplex reaction that coamplifies the fragments together with several highly polymorphic markers, for instance, short tandem repeats. In this work, we successfully included newly designed oligonucleotide primers for the detection of delta F508, the most frequent mutation causing cystic fibrosis, in the commercial AmpFlSTR Profiler Plus PCR Amplification Kit (PE Applied Biosystems). This coamplification enabled us to test the hypothesis of a heterozygote advantage associated with cystic fibrosis-specifically, higher resistance to toxin-mediated diarrheas--in a Sicilian skeletal sample of individuals who died in a cholera epidemic in 1837. The proposed method should also be suitable for the genetic characterization of other slightly polymorphic loci tested on human and animal ancient DNA; it should permit simple authentication of results by comparing the fingerprints obtained from independent amplifications repeated several times.

Chromosome mapping of Miller-Diecker, Smith-Magenis and RARA loci in non-human primates: implications in the evolution of human chromosome 17.

Molecular cytogenetics allows to verify chromosomal homologies previously hypothesised on the base of banding pattern comparison in different species. So far only the chromosome painting technique has been extensively used in studies of chromosomal evolution. This technique allows to detect only interchromosomal rearrangements. Human and Great Apes chromosomes basically differ by intrachromosomal rearrangements, in particular inversions; with chromosome painting it has just been possible to confirm the origin by fusion of human chromosome 2 and a reciprocal translocation in Gorilla, involving the homologous of chromosome 5 and 17. In order to verify intrachromosomal rearrangements in human chromosomal evolution, chromosome mapping of human loci in non-human primates is a useful approach. We mapped Miller-Diecker, Smith-Magenis and RARA loci localised on human chromosome 17, in Gorilla gorilla, Pongo pygmaeus, Macaca fascicularis and Cercopithecus aethiops. On the base of the obtained results it was possible to verify chromosomal rearrangements previously identified by banding, to achieve new informations about the controversial evolution of human chromosome 17, and to detect the occurrence of a paracentric inversion in the homologous in Cercopithecus aethiops.