Precise and in situ genetic humanization of 6 Mb of mouse immunoglobulin genes.

Genetic humanization, which involves replacing mouse genes with their human counterparts, can create powerful animal models for the study of human genes and diseases. One important example of genetic humanization involves mice humanized for their Ig genes, allowing for human antibody responses within a mouse background (HumAb mice) and also providing a valuable platform for the generation of fully human antibodies as therapeutics. However, existing HumAb mice do not have fully functional immune systems, perhaps because of the manner in which they were genetically humanized.

Protein-tyrosine phosphatase H1 controls growth hormone receptor signaling and systemic growth.

Several protein-tyrosine phosphatases (PTPs) have been implicated in the control of growth hormone receptor (GHR) signaling, but none have been shown to affect growth in vivo. We have applied a battery of molecular and cellular approaches to test a family-wide panel of PTPs for interference with GHR signaling. Among the subset of PTPs that showed activity in multiple readouts, we selected PTP-H1/PTPN3 for further in vivo studies and found that mice lacking the PTP-H1 catalytic domain show significantly enhanced growth over their wild type littermates.

Agouti-related protein-deficient mice display an age-related lean phenotype.

Endogenous modulators of the central melanocortin system, such as the agouti-related protein (AgRP), should hold a pivotal position in the regulation of energy intake and expenditure. Despite this, AgRP-deficient mice were recently reported to exhibit normal food intake, body weight gain, and energy expenditure. Here we demonstrate that 2- to 3-month-old Agrp null mice do in fact exhibit subtle changes in response to feeding challenges (fasting and MCR agonists) but, of more significance and magnitude, exhibit reduced body weight and adiposity after 6 months of age.

High-throughput engineering of the mouse genome coupled with high-resolution expression analysis.

One of the most effective approaches for determining gene function involves engineering mice with mutations or deletions in endogenous genes of interest. Historically, this approach has been limited by the difficulty and time required to generate such mice. We describe the development of a high-throughput and largely automated process, termed VelociGene, that uses targeting vectors based on bacterial artificial chromosomes (BACs).

Delayed rRNA processing results in significant ribosome biogenesis and functional defects.

mof6-1 was originally isolated as a recessive mutation in Saccharomyces cerevisiae which promoted increased efficiencies of programmed -1 ribosomal frameshifting and rendered cells unable to maintain the killer virus. Here, we demonstrate that mof6-1 is a unique allele of the histone deacetylase RPD3, that the deacetylase function of Rpd3p is required for controlling wild-type levels of frameshifting and virus maintenance, and that the closest human homolog can fully complement these defects. Loss of the Rpd3p-associated histone deacetylase function, either by mutants of rpd3 or loss of the associated gene product Sin3p or Sap30p, results in a delay in rRNA processing rather than in an rRNA transcriptional defect.