The length of homology required for gene targeting in embryonic stem cells

Homologous recombination has been used to introduce site-specific mutations into murine embryonic stem (ES) cells with both insertion and replacement vectors. In this study, we compared the frequency of gene targeting with various lengths of homology and found a dramatic increase in targeting with an increase in homology from 1.3 to 6.8 kb. We examined in detail the relationship between the length of homology and the gene-targeting frequency for replacement vectors and found that a critical length of homology is needed for targeting. Adding greater lengths of homology to this critical length has less of an effect on the targeting frequency. We also analyzed the lengths of homology necessary on both arms of the vector for gene replacement events and found that 472 bp of homology is used as efficiently as 1.2 kb in the formation and resolution of crossover junctions

Goosecoid acts cell autonomously in mesenchyme-derived tissues during craniofacial development

Mice homozygous for a targeted deletion of the homeobox gene Goosecoid (Gsc) have multiple craniofacial defects. To understand the mechanisms responsible for these defects, the behavior of Gsc-null cells was examined in morula aggregation chimeras. In these chimeras, Gsc-null cells were marked with beta-galactosidase (beta-gal) activity using the ROSA26 lacZ allele. In addition, mice with a lacZ gene that had been introduced into the Gsc locus were used as a guide to visualize the location of Gsc-expressing cells. In Gsc-null\u3c-\u3ewild-type chimeras, tissues that would normally not express Gsc were composed of both Gsc-null and wild-type cells that were well mixed, reflecting the overall genotypic composition of the chimeras. However, craniofacial tissues that would normally express Gsc were essentially devoid of Gsc-null cells. Furthermore, the nasal capsules and mandibles of the chimeras had defects similar to Gsc-null mice that varied in severity depending upon the proportion of Gsc-null cells. These results combined with the analysis of Gsc-null mice suggest that Gsc functions cell autonomously in mesenchyme-derived tissues of the head. A developmental analysis of the tympanic ring bone, a bone that is always absent in Gsc-null mice because of defects at the cell condensation stage, showed that Gsc-null cells had the capacity to form the tympanic ring condensation in the presence of wild-type cells. However, analysis of the tympanic ring bones of 18.5 d.p.c. chimeras suggests that Gsc-null cells were not maintained. The participation of Gsc-null cells in the tympanic ring condensation of chimeras may be an epigenetic phenomenon that results in a local environment in which more precursor cells are present. Thus, the skeletal defects observed in Gsc-null mice may reflect a regional reduction of precursor cells during embryonic development

Implantation and Gastrulation Abnormalities Characterize Early Embryonic Lethal Mouse Lines [preprint]

The period of development between the zygote and embryonic day 9.5 in mice includes multiple developmental milestones essential for embryogenesis. The preeminence of this period of development has been illustrated in loss of function studies conducted by the International Mouse Phenotyping Consortium (IMPC) which have shown that close to one third of all mouse genes are essential for survival to weaning age and a significant number of mutations cause embryo lethality before E9.5. Here we report a systematic analysis of 21 pre-E9.5 lethal lines generated by the IMPC. Analysis of pre- and post-implantation embryos revealed that the majority of the lines exhibit mutant phenotypes that fall within a window of development between implantation and gastrulation with few pre-implantation and no post-gastrulation phenotypes. Our study provides multiple genetic inroads into the molecular mechanisms that control early mammalian development and the etiology of human disease, in particular, the genetic bases of infertility and pregnancy loss. We propose a strategy for an efficient assessment of early embryonic lethal mutations that can be used to assign phenotypes to developmental milestones and outline the time of lethality

On the role of vertical ground heat flux for analytical simulation of borehole heat exchangers

Analytical modelling techniques are frequently used for prediction of the impacts of borehole heat exchangers (BHEs) on the thermal conditions in the subsurface. They are appealing because they are easy to use, compact and computationally efficient. However, analytical formulations also cut down the complexity of the conditions in the field by limited resolution of variations in space and time, and by often simplified specifications of boundary conditions. In this presentation, we focus on the definition of the land surface boundary condition in line source solutions. As BHEs are thin elongated forms that can be approximated by a linear shape function, main attention is on the radial heat transfer, but less on the axial effects. Given the long operation time, however, the sharp physical boundary at the top may exert a substantial influence on the temperature evolution in the shallow ground and thus influence the performance of the ground source heat pump. We examine different formulations with Dirichlet and Cauchy type boundaries included in the line source equation, with and without horizontal groundwater flow. Both homogeneous as well as inhomogeneous implementations are presented, which offer new flexibilities for simulation of nonuniform land surface impacts such as associated with varying land use types. The presented approach also facilitates to account for the accelerated ground heat flux due to global warming and due to urbanization such as observed in so-called subsurface urban heat islands in many cities

Goosecoid is not an essential component of the mouse gastrula organizer but is required for craniofacial and rib development

Goosecoid (gsc) is an evolutionarily conserved homeobox gene expressed in the gastrula organizer region of a variety of vertebrate embryos, including zebrafish, Xenopus, chicken and mouse. To understand the role of gsc during mouse embryogenesis, we generated gsc-null mice by gene targeting in embryonic stem cells. Surprisingly, gsc-null embryos gastrulated and formed the primary body axes; gsc-null mice were born alive but died soon after birth with numerous craniofacial defects. In addition, rib fusions and sternum abnormalities were detected that varied depending upon the genetic background. Transplantation experiments suggest that the ovary does not provide gsc function to rescue gastrulation defects. These results demonstrate that gsc is not essential for organizer activity in the mouse but is required later during embryogenesis for craniofacial and rib cage development

EVALUACIÓN DE RENDIMIENTO EN BIOMASA DE CUATRO CULTIVARES DE MAÍZ: CASO DE LA CUENCA BAJA DEL RÍO PURIO, PROVINCIA DE LOS SANTOS, AÑO 2021

El objetivo principal de esta investigación fue evaluar el rendimiento en biomasa de cuatro cultivares de maíz. Realizada en la Finca Aranda, Corregimiento de Pocrí, Distrito de Pocrí, Provincia de los Santos, en época de lluvia. Para este fin, inicialmente, se realiza la caracterización morfoclimática y se estiman las curvas de agresividad climática de la lluvia a través del índice   modificado de Fournier (IMF), ajustadas a la subcuenca del río Purio. Posteriormente, se evaluaron los cultivares de maíz P30-F35, SV 1020, IDIAP 1102 y ADV 9293. Implementado un diseño de boques completos al azar (DBCA), con cuatro tratamientos y cinco bloques o repeticiones. Como resultado se obtuvo que, el espacio que comprende la cuenca media y alta del río Purio expone valores estimados muy altos de agresividad climática >160; mientras que, la cuenca baja registra valores considerados altos >120 y <160. No obstante, para la variable rendimiento en biomasa el cultivar P30-F35 obtuvo la mayor media con 28 Kg, seguido del SV 1020 con 26 Kg, el ADV 9293 24 Kg y el IDIAP 1102 con 22 Kg. Concluyendo al no existir diferencia significativa, la elección del cultivar a utilizar está sujeta al costo de semilla en el mercado y el nivel tecnológico de cultivo