Igor L. Goldman

Fused in Sarcoma (FUS) Protein Lacking Nuclear Localization Signal (NLS) and Major RNA Binding Motifs Triggers Proteinopathy and Severe Motor Phenotype in Transgenic Mice

Background: FUS inclusions are hallmarks of certain neurodegenerative diseases. Results: Expression of a highly aggregate prone FUS variant in transgenic mice causes proteinopathy and severe motor phenotype. Conclusion: Aggregation of FUS is sufficient to recapitulate motor pathology typical for amyotrophic lateral sclerosis. Significance: Understanding the role of protein aggregation in the development of human neurodegenerative diseases is crucial for designing efficient therapeutic approaches. Dysfunction of two structurally and functionally related proteins, FUS and TAR DNA-binding protein of 43 kDa (TDP-43), implicated in crucial steps of cellular RNA metabolism can cause amyotrophic lateral sclerosis (ALS) and certain other neurodegenerative diseases. The proteins are intrinsically aggregate-prone and form non-amyloid inclusions in the affected nervous tissues, but the role of these proteinaceous aggregates in disease onset and progression is still uncertain. To address this question, we designed a variant of FUS, FUS 1–359, which is predominantly cytoplasmic, highly aggregate-prone, and lacks a region responsible for RNA recognition and binding. Expression of FUS 1–359 in neurons of transgenic mice, at a level lower than that of endogenous FUS, triggers FUSopathy associated with severe damage of motor neurons and their axons, neuroinflammatory reaction, and eventual loss of selective motor neuron populations. These pathological changes cause abrupt development of a severe motor phenotype at the age of 2.5–4.5 months and death of affected animals within several days of onset. The pattern of pathology in transgenic FUS 1–359 mice recapitulates several key features of human ALS with the dynamics of the disease progression compressed in line with shorter mouse lifespan. Our data indicate that neuronal FUS aggregation is sufficient to cause ALS-like phenotype in transgenic mice.

Transgenic Goats in the World Pharmaceutical Industry of the 21st Century

In many developed countries, isolation of human pharmaceutical proteins from milk of genetically modified animals is currently a priority. One of the first commercial pharmaceuticals obtained from the milk of transgenic goats, an anticoagulant antithrombin III, developed by Genzyme Transgenic Corporation, an American biotechnological company, will appear on the pharmaceutical market in the nearest future. In this review, we discuss the role of fundamental science in the development of this field of the pharmaceutical industry.

Early lethality and neuronal proteinopathy in mice expressing cytoplasm-targeted FUS that lacks the RNA recognition motif.

Mutations to the RNA binding protein, fused in sarcoma (FUS) occur in ∼5% of familial ALS and FUS-positive cytoplasmic inclusions are commonly observed in these patients. Altered RNA metabolism is increasingly implicated in ALS, yet it is not understood how the specificity with which FUS interacts with RNA in the cytoplasm can affect its aggregation in vivo. To further understand this, we expressed, in mice, a form of FUS (FUS ΔRRMcyt) that lacked the RNA recognition motif (RRM), thought to impart specificity to FUS-RNA interactions, and carried an ALS-associated point mutation, R522G, retaining the protein in the cytoplasm. Here we report the phenotype and results of histological assessment of the brain of transgenic mice expressing this isoform of FUS. Results demonstrated that neuronal expression of FUS ΔRRMcyt caused early lethality often preceded by severe tremor. Large FUS-positive cytoplasmic inclusions were found in many brain neurons; however, neither neuronal loss nor neuroinflammatory response was observed. In conclusion, the extensive FUS proteinopathy and severe phenotype of these mice suggests that affecting the interactions of FUS with RNA in vivo may augment its aggregation in the neuronal cytoplasm and the severity of disease processes.

Expression of full-length human pro-urokinase in mammary glands of transgenic mice

Human pro-urokinase expressed in the mammary glands of transgenic animals is quickly activated and converted to urokinase by proteases that are present in the milk. Thus, it is nearly impossible to isolate full-sized pro-urokinase from the milk of transgenic animals. To solve this problem, we constructed transgenic mice that express human pro-urokinase and modified ecotin, which is a potent serine protease inhibitor from E. coli, in their mammary glands. The gene encoding ecotin was modified so as to enhance its specificity for the human urokinase-type plasminogen activator. Co-expression of modified ecotin and human pro-urokinase in the mammary glands allows for purification of full-length human pro-urokinase from these transgenic mice. The results described here suggest a general way of preventing the activation of zymogens that are expressed in the mammary glands of transgenic animals by co-expression of a zymogen along with a protease inhibitor.

The state of health and the reproductive potential of transgenic mice secreting recombinant human lactoferrin in milk.

Maintenance of transgenic animals’ health and preservation of their reproduction is of primary importance for their long-term use as bioreactors of human medicinal proteins. It is known that many human bioactive proteins may have similar physiological effects in animals. To obtain transgenic animals secreting human medicinal proteins with milk, tissue-specific promoters are used in genetic engineering. The reproductive ability of transgenic animals is disturbed only if integration of a foreign genetic material into the animal genome results in injuries (insertions) in the DNA regions that are associated with the reproductive function. Insertions may also change any other important genomic regions of transgenic animals. To be used in practice, transgenic animals should ensure economically significant production of proteins of interest with milk. These issues were studied in a model experiment in mice transgenic for the human lactoferrin gene. Mouse strains were obtained by breeding the primary transgenic animals transmitting the transgene with a high level of production of this protein with milk. The initial strains are characterized by a normal reproductive ability, correspond to the physiological norm characteristic for this animal species, and retain these characteristics (including the level of human lactoferrin production in milk) in a series of generations. Lactoferrin is a human breast milk protein that protects a newborn from intestinal infections until it develops an own mechanism of immunological defense [1‐ 3]. Obtaining this human protein with milk farm animals being used as bioreactors will make it possible to create an adequate nutrition for artificially fed infants. The bactericidal properties of human lactoferrin are promising for creating a wide spectrum of highly efficient and biologically safe drugs of a new generation [4‐6].

Gamma-carboline inhibits neurodegenerative processes in a transgenic model of amyotrophic lateral sclerosis

189 Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative disease caused by the selective death of motor neurons. An important component in the ALS pathogenesis is the aggregation of proteins prone to conformational changes and the formation of characteristic intracellular histopathological inclu sions, on the basis of which this disease was attributed to the group of proteopathies [1]. In addition to the already known gene SOD1, recent medical genetic studies have identified a number of other genes whose mutations lead to the formation of pathogenic forms of their encoded proteins and development a neurode generative process with motoneuron lesions [2]. In the sporadic ALS forms, these proteins were also found in the histopathological inclusions of the autopsy material of ALS patients. Moreover, studies performed in experimental models of ALS in trans genic mice and cell cultures provided evidence that the pathological picture of proteopathy characteristic of ALS can be reproduced in the case of metabolic disor der of only one of the key proteins [3]. When studying the mechanisms of proteopathies associated with ALS and frontotemporal degenera tion, a new type of molecular cellular pathology was described. This pathology is caused by the dysfunction of the DNA/RNA binding proteins TDP43 and FUS (fused in sarcoma), which results in the inability of these proteins to form physiologically active, easily dissociating complexes with RNA (RNP). Instead, these proteins form stable RNA free structures with stably deposited aggregated forms of TDP43 and FUS proteins. This process is accompanied by changes in the intracellular compartmentalization of TDP43 and FUS and their accumulation in the pathogenic inclu sions in the cytoplasm [4–7].

Effect of DNA loop anchorage regions (LARs) and microinjection timing on expression of β‐galactosidase gene injected into one‐cell rabbit embryos

The conditions favoring expression of a reporter gene microinjected into a male pronucleus of naturally ovulated and fertilized rabbit eggs have been studied. Injection of the reporter gene during S phase of the cell‐cycle allows the highest level of expression of the gene. Incorporation of DNA loop anchorage regions (LARs) into constructs upstream and/or downstream of the reporter gene significantly increased the efficiency of expression. In all cases the expression of the microinjected gene started after a period of transcriptional quiescence, i.e., together with the expression of the host genome. Correct targeting of microinjected constructs within the nuclei via interaction of LAR elements with receptor sites on the nucleoskeleton may facilitate expression of injected DNA constructs as well as their integration into host cell DNA.

Heterologous CpG island becomes extensively methylated in the genome of transgenic mice

It is demonstrated that a heterologous (chicken) CpG island containing five Sp1 canonical recognition sequences becomes highly methylated in the genome of transgenic mice bearing one or several copies of the transgene. Similar levels of methylation of the chicken CpG island were observed in different tissues of transgenic mice except the brain where the level of methylation of this chicken CpG‐rich fragment was significantly lower than in other tissues. Analysis of susceptibility of the “transgenic” CpG island to Hpa II and Msp I restriction nucleases revealed an unusual methylation pattern interfering with the action of both of these enzymes. A conclusion has been drawn that heterologous CpG island per se does not contain all necessary signals permitting to maintain its own non‐methylated status in the genome of transgenic animals.