SummaryPolyploidy events have played an important role in the evolution of angiosperm genomes. Here, we demonstrate how genomic histories can increase phylogenetic resolution in a gene family, specifically the expansin superfamily of cell wall proteins. There are 36 expansins in Arabidopsis and 58 in rice. Traditional sequence-based phylogenetic trees yield poor resolution below the family level. To improve upon these analyses, we searched for gene colinearity (microsynteny) between Arabidopsis and rice genomic segments containing expansin genes. Multiple rounds of genome duplication and extensive gene loss have obscured synteny. However, by simultaneously aligning groups of up to 10 potentially orthologous segments from the two species, we traced the history of 49 out of 63 expansin-containing segments back to the ancestor of monocots and eudicots. Our results indicate that this ancestor had 15-17 expansin genes, each ancestral to an extant clade. Some clades have strikingly different growth patterns in the rice and Arabidopsis lineages, with more than half of all rice expansins arising from two ancestral genes. Segmental duplications, most of them part of polyploidy events, account for 12 out of 21 new expansin genes in Arabidopsis and 16 out of 44 in rice. Tandem duplications explain most of the rest. We were also able to estimate a minimum of 28 gene deaths in the Arabidopsis lineage and nine in rice. This analysis greatly clarifies expansin evolution since the last common ancestor of monocots and eudicots and the method should be broadly applicable to many other gene families.

Expansins comprise a superfamily of plant cell wall-loosening proteins that has been divided into four distinct families, EXPA, EXPB, EXLA and EXLB. In a recent analysis of Arabidopsis thaliana and Oryza sativa expansins, we proposed a further subdivision of the families into 17 clades, representing independent lineages in the last common ancestor of monocots and eudicots. This division was based on both traditional sequence-based phylogenetic trees and on position-based trees, in which genomic locations and dated segmental duplications were used to reconstruct gene phylogeny. In this article we review recent work concerning the patterns of expansin evolution in angiosperms and include additional insights gained from the genome of a second eudicot species, Populus trichocarpa, which includes at least 36 expansin genes. All of the previously proposed monocot-eudicot orthologous groups, but no additional ones, are represented in this species. The results also confirm that all of these clades are truly independent lineages. Furthermore, we have used position-based phylogeny to clarify the history of clades EXPA-II and EXPA-IV. Most of the growth of the expansin superfamily in the poplar lineage is likely due to a recent polyploidy event. Finally, some monocot-eudicot clades are shown to have diverged before the separation of the angiosperm and gymnosperm lineages.

Intraoperative fluoroscopy can be an effective, easy, and safe method for improving tunnel positioning during ACL reconstruction.

The EXPA genes of Physcomitrella are likely to have maintained the same biochemical function as angiosperm expansins despite their independent evolutionary history. Changes seen at normally conserved residues in the Physcomitrella EXPB family suggest a possible change in function as one mode of evolution in this family.

In this paper, we present a new methodology for subject-specific finite element modeling of the tibiofemoral joint based on in vivo computed tomography (CT), magnetic resonance imaging (MRI), and dynamic stereo-radiography (DSX) data. We implemented and compared two techniques to incorporate in vivo skeletal kinematics as boundary conditions: one used MRI-measured tibiofemoral kinematics in a nonweight-bearing supine position and allowed five degrees of freedom (excluding flexion-extension) at the joint in response to an axially applied force; the other used DSX-measured tibiofemoral kinematics in a weight-bearing standing position and permitted only axial translation in response to the same force. Verification and comparison of the model predictions employed data from a meniscus transplantation study subject with a meniscectomized and an intact knee. The model-predicted cartilage-cartilage contact areas were examined against "benchmarks" from a novel in situ contact area analysis (ISCAA) in which the intersection volume between nondeformed femoral and tibial cartilage was characterized to determine the contact. The results showed that the DSX-based model predicted contact areas in close alignment with the benchmarks, and outperformed the MRI-based model: the contact centroid predicted by the former was on average 85% closer to the benchmark location. The DSX-based FE model predictions also indicated that the (lateral) meniscectomy increased the contact area in the lateral compartment and increased the maximum contact pressure and maximum compressive stress in both compartments. We discuss the importance of accurate, task-specific skeletal kinematics in subject-specific FE modeling, along with the effects of simplifying assumptions and limitations.