Transgenic animal model of bone mass modulation

Abstract

The present invention relates to methods and materials used to express the HBM protein in animal cells and transgenic animals. The present invention also relates to transgenic animals expressing the high bone mass gene, the corresponding wild-type gene, and mutants thereof. The invention provides nucleic acids, including coding sequences, oligonucleotide primers and probes, proteins, cloning vectors, expression vectors, transformed hosts, methods of developing pharmaceutical compositions, methods of identifying molecules involved in bone development, and methods of diagnosing and treating diseases involved in bone development. In preferred embodiments, the present invention is directed to methods for treating, diagnosing and preventing osteoporosis.

Description

[0001]This application claims priority to International Application No. PCT / US02 / 14876, filed May 13, 2002, and the benefit of Provisional Application Nos. 60 / 290,071 filed May 11, 2001; 60 / 291,311 filed May 17, 2001; 60 / 353,058 filed Feb. 1, 2002, and 60 / 361,293 filed Mar. 4, 2002, the disclosures of each are herein incorporated by reference in their entirety for all purposes.FIELD OF THE INVENTION[0002]The present invention relates generally to the field of genetics, genomics and molecular biology. The invention relates to methods and materials used to isolate, detect and sequence a high bone mass gene and corresponding wild-type gene, and mutants thereof. The present invention also relates to the high bone mass (HBM) gene, the corresponding wild-type gene, and mutants thereof. The genes identified in the present invention are implicated in the ontology and physiology of bone development. The invention also provides nucleic acids, proteins, cloning vectors, expression vectors, tra...

AI Technical Summary

Benefits of technology

[0019]The present invention describes the identification of the LRP5 gene and the HBM allele of the LRP5 gene on chromosome 11q13.3 by genetic linkage and mutation analysis. The LRP5 gene and the LRP5 protein which it encodes have previously been referred to as Zmax1 and Zmax1 (also Zmax) by the inventors and coworkers. The gene and its product have also been referred to by others using the designation LR3. It is understood that Zmax, Zmax1, LRP5, and LR3 are synonymous terms. The use of genetic markers linked to the genes has aided their discovery. By using linkage analysis and mutation analysis, persons predisposed to HBM may be readily identified. Cloning methods using Bacterial Artificial Chromosomes have enabled the inventors to focus on the chromosome region of 11q13.3 and to accelerate the sequencing of the autosomal dominant gene. In addition, the invention identifies the LRP5 gene and the HBM gene, and identifies the guanine-to-thymine polymorphism mutation at position 582 in the LRP5 gene that produces the HBM gene and the HBM phenotype.

[0020]The present invention identifies the LRP5 gene and the HBM gene, which can be used to determine if people are predisposed to HBM and, therefore, not susceptible to diseases characterized by reduced bone density, including, for example, osteoporosis, or are predisposed and susceptible to diseases characterized by abnormally high bone density, such as, for example, osteopetrosis. Older individuals carrying the HBM gene express the HBM protein, and, therefore, do not develop osteoporosis. In other words, the HBM gene is a suppressor of osteoporosis. This in vivo observation is a strong evidence that treatment of normal individuals with the HBM gene or protein, or fragments thereof, will ameliorate osteoporosis.

[0056]In alternative aspects of this method, a group of animals may alternatively comprise a promoter region operably linked to a transgenic sequence encoding LRP5, LRP6, HBM, or a variant thereof as described herein. Such methods are useful, for example, for screening experimental procedures to identify one or more compounds that replicate the HBM phenotype in a non-HBM animal, or to identify combinations of compounds and experimental procedures that can function synergistically to enhance the HBM effect.

[0058]This method can further comprise a step of administering a test compound to at least some of the animals prior to measuring at least one parameter of bone development in the animals, and / or further comprising a step of administering an experimental procedure to at least some of the animals prior to measuring at least one parameter of bone development in the animals. The test compound can be administered, for example, by injection, orally, by suppositories, in an implant, or topically. The experimental procedure can be chosen, for example, from among an ovariectomy, restricted bone loading, and increased bone loading. The test compound can comprise, for example, a hormone, a growth factor, a peptide, an RNA, a DNA, a mineral, a vitamin, a natural product, or a synthetic organic compound. The experimental procedure can comprise a surgical procedure, a gene therapy procedure, a drug therapy procedure, a dietary regimen, or physical exercise.

Problems solved by technology

Osteoporosis affects men as well as women, and, taken with other abnormalities of bone, presents an ever-increasing health risk for an aging population.

This rapid loss is generally associated with an increase of bone resorption and formation.

However, the resorptive cycle is more dominant and the result is a net loss of bone mass.

The results of osteoporosis are both personally harmful, and also account for a large economic loss due to its chronicity and the need for extensive and long-term support hospitalization and nursing home care) from the disease sequelae.

Although this therapy frequently is successful, patient compliance is low, primarily due to the undesirable side-effects of chronic estrogen treatment.

This protocol is similar to that which is used in birth control regimens, and often is not tolerated by women because of the side-effects characteristic of progestin.

The use of calcitonin has been somewhat limited, however.

Its effects are very modest in increasing bone mineral density and the treatment is very expensive.

Senile osteoporosis is similar to postmenopausal osteoporosis in that it is marked by the loss of bone mineral density and resulting increase in fracture rate, morbidity, and associated mortality.

Treatment of this disease has not been very satisfactory.

These studies are difficult because bone mass (the phenotype) is a continuous, quantitative, polygenic trait, and is confounded by environmental factors such as nutrition, co-morbid disease, age, physical activity, and other factors.

Also, this type of study design requires large numbers of subjects.

In particular, the results of VDR studies to date have been confusing and contradictory (Garnero et al., J.

Furthermore, the work thus far has not shed much light on the mechanisms) whereby the genetic influences might exert their effect on bone mass.

While it is well known that peak bone mass is largely determined by genetic rather than environmental factors, studies to determine the gene loci (and ultimately the genes) linked to variation in bone mass are difficult and expensive.

However, genetic linkage studies involving bone mass are hampered by two major problems.

The first problem is the phenotype, as discussed briefly above.

Bone mass is a continuous, quantitative trait, and establishing a discrete phenotype is difficult.

The second problem is the age component of the phenotype.

By the time an individual can be identified as having low bone mass, there is a high probability that their parents or other members of prior generations will be deceased and therefore unavailable for study, and younger generations may not have even reached peak bone mass, making their phenotyping uncertain for genetic analysis.

However, few markers are sufficiently polymorphic as to be informative in all those individuals.

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