Screening ethnically diverse human embryonic stem cells identifies a chromosome 20 minimal amplicon conferring growth advantage

The International Stem Cell Initiative analyzed 125 human embryonic stem (ES) cell lines and 11 induced pluripotent stem (iPS) cell lines, from 38 laboratories worldwide, for genetic changes occurring during culture. Most lines were analyzed at an early and late passage. Single-nucleotide polymorphism (SNP) analysis revealed that they included representatives of most major ethnic groups. Most lines remained karyotypically normal, but there was a progressive tendency to acquire changes on prolonged culture, commonly affecting chromosomes 1, 12, 17 and 20. DNA methylation patterns changed haphazardly with no link to time in culture. Structural variants, determined from the SNP arrays, also appeared sporadically. No common variants related to culture were observed on chromosomes 1, 12 and 17, but a minimal amplicon in chromosome 20q11.21, including three genes expressed in human ES cells, ID1, BCL2L1 and HM13, occurred in >20% of the lines. Of these genes, BCL2L1 is a strong candidate for driving culture adaptation of ES cells

Governance and Agricultural Production Efficiency: A Cross-Country Aggregate Frontier Analysis

"This study uses a stochastic frontier approach to investigate the relationship between six governance indicators and agricultural efficiency. We find that improvements in rule of law, control of corruption and government effectiveness enhance agricultural productivity significantly if each indicator enters the inefficiency equation independently. When all six indicators are included in the equation, we find that an improvement in rule of law raises agricultural efficiency significantly, but increases in voice and accountability and political stability appear to significantly reduce agricultural efficiency. Grouping the six indicators into three dimensions, we find that an improvement in 'respect for institutional framework' raises agricultural efficiency significantly, but an enhancement in 'selection of authority' reduces agricultural efficiency significantly. Our results imply that poorer countries can enhance their agricultural efficiency substantially by strengthening the state and citizens' respect for institutional framework. However, our results show that greater democracy is associated with lower agricultural efficiency. This finding is consistent with interest group capture and political failure arguments of the political economy literature." Copyright (c) 2008 The Authors. Journal compilation (c) 2008 The Agricultural Economics Society.