The Effects of Lead-Vehicle Size on Driver Following Behavior: Is Ignorance Truly Bliss?

The objective of this study was to examine whether size of a lead vehicle (passenger car or light truck) affects the distance at which following vehicles travel. Naturalistic following data were collected from drivers using instrumented passenger cars in place of their own vehicles. The results show that these drivers followed light trucks at shorter distances than they followed other passenger cars by an average of 5.6 m, or .19 s in headway time margin, but at the same velocities and range-rates. This result is discussed in the context of a passenger car driver’s ability to see beyond a lead vehicle to assess, and respond to, the status of traffic downstream. The results of this study suggest that knowing the state of traffic beyond the lead vehicle, even by only one additional vehicle, affects gap length. Specifically, it appears that when dimensions of lead vehicles permit other drivers to see through, over, or around them, drivers maintain significantly longer (i.e., safer) distances

The birth of a human-specific neural gene by incomplete duplication and gene fusion

Background: Gene innovation by duplication is a fundamental evolutionary process but is difficult to study in humans due to the large size, high sequence identity, and mosaic nature of segmental duplication blocks. The human-specific gene hydrocephalus-inducing 2, HYDIN2, was generated by a 364 kbp duplication of 79 internal exons of the large ciliary gene HYDIN from chromosome 16q22.2 to chromosome 1q21.1. Because the HYDIN2 locus lacks the ancestral promoter and seven terminal exons of the progenitor gene, we sought to characterize transcription at this locus by coupling reverse transcription polymerase chain reaction and long-read sequencing. Results: 5' RACE indicates a transcription start site for HYDIN2 outside of the duplication and we observe fusion transcripts spanning both the 5' and 3' breakpoints. We observe extensive splicing diversity leading to the formation of altered open reading frames (ORFs) that appear to be under relaxed selection. We show that HYDIN2 adopted a new promoter that drives an altered pattern of expression, with highest levels in neural tissues. We estimate that the HYDIN duplication occurred ~3.2 million years ago and find that it is nearly fixed (99.9%) for diploid copy number in contemporary humans. Examination of 73 chromosome 1q21 rearrangement patients reveals that HYDIN2 is deleted or duplicated in most cases. Conclusions: Together, these data support a model of rapid gene innovation by fusion of incomplete segmental duplications, altered tissue expression, and potential subfunctionalization or neofunctionalization of HYDIN2 early in the evolution of the Homo lineage

Gene expression profiling in human craniosynostoses: a tool to investigate the molecular basis of suture ossification

Non-sy ndromic craniosy nostoses (NSC) occur as isolated skull malf ormations due to the premature ossif ication of one (single suture f orms) or more (complex f orms) calv arial sutures and represent the most f requent f orm of craniosy nostosis worldwide. The etiology of NSC is still largely unknown, as a genetic basis can be rarely demonstrated especially in single-suture f orms. In these cases, during the prenatal/perinatal dev elopment of af f ected patients, only one suture undergoes a premature direct ossif ication within an otherwise phy siologically grown skull. This could suggest that def inite somatic alterations, possibly due to unclear env ironmental agents, occur locally at the site of premature suture f usion during skull dev elopment. A promising tool to inv estigate the molecular mechanisms that may orchestrate this ev ent is the comparativ e analy sis of suture- and sy nostosis-deriv ed tissues and cells. Particularly , this rev iew will f ocus on the dif f erent studies that attempted to clarif y this issue using genome-wide microarray -based technologies f or the comparativ e analy sis of gene expression prof iles. All relev ant results will be comprehensiv ely rev iewed, possibly compared and critically discussed