Mitochondrial population genomics supports a single pre-Clovis origin with a coastal route for the peopling of the Americas

It is well accepted that the Americas were the last continents reached by modern humans, most likely through Beringia. However, the precise time and mode of the colonization of the New World remain hotly disputed issues. Native American populations exhibit almost exclusively five mitochondrial DNA (mtDNA) haplogroups (A-D and X). Haplogroups A-D are also frequent in Asia, suggesting a northeastern Asian origin of these lineages. However, the differential pattern of distribution and frequency of haplogroup X led some to suggest that it may represent an independent migration to the Americas. Here we show, by using 86 complete mitochondrial genomes, that all Native American haplogroups, including haplogroup X, were part of a single founding population, thereby refuting multiple-migration models. A detailed demographic history of the mtDNA sequences estimated with a Bayesian coalescent method indicates a complex model for the peopling of the Americas, in which the initial differentiation from Asian populations ended with a moderate bottleneck in Beringia during the last glacial maximum (LGM), around similar to 23,000 to similar to 19,000 years ago. Toward the end of the LGM, a strong population expansion started similar to 18,000 and finished similar to 15,000 years ago. These results support a pre-Clovis occupation of the New World, suggesting a rapid settlement of the continent along a Pacific coastal route.

Clonal Complex Chromosome Aberration in Non-Ossifying Fibroma

Cytogenetic information of non-ossifying fibromas (NOFs) is exceptionally limited. This fact relies, in part, on their benign nature but mainly because most cases evolve undetected or there is no need for surgical intervention. We report the case of a NOF arising in the left tibia of a 14-year-old male with an invariable clonal translocation. The karyotype was denoted as 42-46,XY,t(11;3;14)(q23;p21;p11). There are only two previous reported cases of clonally aberrant NOF. Records from additional cases will be essential to assess whether consistent karyotypic aberrations define this lesion. Pediatr Blood Cancer 2010;54:764 767. (C) 2010 Wiley-Liss, Inc.

Cryptic SYT/SXX1 fusion gene in high-grade biphasic synovial sarcoma with unique complex rearrangement and extensive BCL2 overexpression

Synovial sarcomas are high-grade malignant mesenchymal tumors that account for 10% of all soft-tissue sarcomas. Almost 95% of these tumors are characterized by a nonrandom chromosomal abnormality, t(X;18)(p11.2;q11.2), that is observed in both biphasic and monophasic variants. In this article, we present the case of a 57-year-old woman diagnosed with high-grade biphasic synovial sarcoma in which conventional cytogenetic analysis revealed the constant presence of a unique t(18;22)(q12;q13), in addition to trisomy 8. The rearrangement was confirmed by fluorescence in situ hybridization. The use of the whole chromosome painting probes WCPX did not detect any rearrangements involving chromosome X, although reverse-transcriptase polymerase chain reaction (PCR) analysis demonstrated the conspicuous presence of a SYT/SXX1 fusion gene. Spectral karyotyping (SKY) was also performed and revealed an insertion of material from chromosome 18 into one of the X chromosomes at position Xp11.2. Thus, the karyotype was subsequently interpreted as 47,X,der(X)ins(X;18) (p11.2;q11.2q11.2),der(18)del(18)(q11.2q11.2)t(18;22)(q12;q13),der(22)t(18;22). Real-time PCR analysis of BCL2 expression in the tumor sample showed a 433-fold increase. This rare finding exemplifies that thorough molecular-cytogenetic analyses are required to elucidate complex and/or cryptic tumor-specific translocations. (C) 2010 Elsevier Inc. All rights reserved.