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Bub3 gene disruption in mice has been studied. The study shows that there is an essential mitotic spindle checkpoint function in early embryogenesis. Bub3-null embryos seem to be normal to day 3.5 postcoitus. In days 4.5-6.4 they accumulate mitotic errors. Null embryos treated with a spindle depolymerizing agent do not arrest in metaphase. Mitotic disorganization is seen.

Homozygous disruption of the transforming growth factor alpha (TGFalpha) in mice results in animals with abnormal skin architecture, wavy hair, curly whiskers while many develop corneal inflammation. This phenotype is quite similar to that of the mice mutant waved-1 (wa-1). Crossing TGFalpha -/- and wa-1 mice result in offspring with the curly whisker-coat phenotype suggesting that the wa-1 phenotype results from a mutation in the TGFalpha gene. TGFalpha must be involved in determining and regulating skin architecture and hair development.

Studies the biological importance and functional role of the chromosomal passenger protein Incenp in mice. Generation of Incenp null embryonic stem cells; Phenotype of Incenp gene disruption; Effect of the phenotype on the microtubule modulation.

Abstract: Accurate animal models that recapitulate the phenotype and genotype of patients with β-thalassemia would enable the development of a range of possible therapeutic approaches. Here we report the generation of a mouse model carrying the codons 41–42 (−TTCT) β-thalassemia mutation in the intact human β-globin locus. This mutation accounts for approximately 40% of β-thalassemia mutations in southern China and Thailand. We demonstrate a low level of production of γ-globins from the mutant locus in day 18 embryos, as well as production of mutant human β-globin mRNA. However, in contrast to transgenic mice carrying the normal human β-globin locus, 4-bp deletion mice fail to show any phenotypic complementation of the knockout mutation of both murine β-globin genes. Our studies suggest that this is a valuable model for gene correction in hemopoietic stem cells and for studying the effects of HbF inducers in vivo in a “humanized” thalassemic environment. [Copyright &y& Elsevier]

Methylmalonic aciduria is a human autosomal recessive disorder of organic acid metabolism resulting from a functional defect in the activity of the enzyme methylmalonyl-CoA mutase. Based upon the homology of the human mutase locus with the mouse locus, we have chosen to disrupt the mouse mutase locus within the criticai CoA binding domain using gene-targeting techniques to create a mouse model of methylmalonic aciduria. The phenotype of homozygous knock-out mice (mut[sup -/-]) is one of early neonatal lethality. Mice appear phenotypically normal at birth and are indistinguishable from littermates. By 15 h of age, they develop reduced movement and suckle less. This is followed by the development of abnormal breathing, and all of the mice with a null phenotype die by 24 h of age. Urinary levels of methylmalonic and methylcitric acids are grossly increased. Measurement of acylcarnitines in blood shows elevation of propionylcarnitine with no change in the levels of acetylcarnitine and free carnitine. Incorporation of [[sup 14]C]propionate in primary fibroblast cultures from mut[sup -/-] mice is reduced to approximately 6% of normal level, whereas there is no detectable synthesis of mut mRNA in the liver. This is the first mouse model that recapitulates the key phenotypic features of mut[sup 0] methylmalonic aciduria. [ABSTRACT FROM AUTHOR]

An abstract of the article "Transgenic Genomic Reporter Assays for Functional Studies and Stem Cell Therapy," by Joseph P. Sarsero and colleagues is presented.

Mitotic spindle checkpoint proteins have been shown to play a crucial role in the accurate segregation of chromosomes during cell division. Bub3 is a member of a group of mitotic checkpoint proteins that are essential for this process. To investigate the role of Bub3 in chromosome segregation and cancer development, we analyzed haploinsufficient cells in mice. Heterozygous Bub3 embryonic fibroblasts displayed increased aneuploidy and premature sister-chromatid separation. In addition, when challenged with the microtubule disruptor nocodazole, the cells showed a slight increase in chromatid breakage and a decrease in the mitotic index. No substantial differences were observed between wild-type and Bub3 heterozygous mice in the frequency or the rate at which tumors appeared. Crossing Bub3(+/-) mice onto a heterozygous tumor-suppressor background of Trp53 or Rb1 similarly revealed no substantial differences in either the number or the rate at which tumors appeared. These results suggest that haploinsufficiency of Bub3 causes a slight increase in chromosome instability but is not clearly associated with a noticeable rise in the probability of tumor formation in the animal, possibly because of a partially functional mitotic checkpoint, or cells exhibiting chromosome instability could have activated the apoptosis pathway and thus escaped tumor induction and detection., ((c) 2005 Wiley-Liss, Inc.)

Accurate animal models that recapitulate the phenotype and genotype of patients with beta-thalassemia would enable the development of a range of possible therapeutic approaches. Here we report the generation of a mouse model carrying the codons 41-42 (-TTCT) beta-thalassemia mutation in the intact human beta-globin locus. This mutation accounts for approximately 40% of beta-thalassemia mutations in southern China and Thailand. We demonstrate a low level of production of gamma-globins from the mutant locus in day 18 embryos, as well as production of mutant human beta-globin mRNA. However, in contrast to transgenic mice carrying the normal human beta-globin locus, 4-bp deletion mice fail to show any phenotypic complementation of the knockout mutation of both murine beta-globin genes. Our studies suggest that this is a valuable model for gene correction in hemopoietic stem cells and for studying the effects of HbF inducers in vivo in a "humanized" thalassemic environment.

Both nuclear and mitochondrial DNA mutations can cause energy generation disorders. Respiratory chain complex I deficiency is the most common energy generation disorder and a frequent cause of infantile mitochondrial encephalopathies such as Leigh's disease and lethal infantile mitochondrial disease. Most such cases have been assumed to be caused by nuclear gene defects, but recently an increasing number have been shown to be caused by mutations in the mitochondrially encoded complex I subunit genes ND4, ND5, and ND6. We report the first four cases of infantile mitochondrial encephalopathies caused by mutations in the ND3 subunit gene. Three unrelated children have the same novel heteroplasmic mutation (T10158C), only the second mutation reported in ND3, and one has the previously identified T10191C mutation. Both mutations cause disproportionately greater reductions in enzyme activity than in the amount of fully assembled complex I, suggesting the ND3 subunit plays an unknown but important role in electron transport, proton pumping, or ubiquinone binding. Three cases appear to have a de novo mutation, with no mutation detected in maternal relatives. Mitochondrial DNA disease may be considerably more prevalent in the pediatric population than currently predicted and should be considered in patients with infantile mitochondrial encephalopathies and complex I deficiency.