From the Archives, in Recognition of the 75th Anniversary of AALAS: “The So-Called Swiss Mouse” by Clara J. Lynch (1969)

Glen Otto

doi:10.30802/AALAS-JAALAS-24-125

Commentary

The AALAS journals have provided a home for a long string of laboratory animal-focused review articles over the years. Some of these articles have been submitted by prominent research scientists who generally publish in more mainstream journals but understand the importance of the Association’s specialty interest in laboratory animal topics such as research animal genetics, nomenclature, and breeding strategies. It is important for all involved in vertebrate research to understand these concepts to ensure that the best animal models can be chosen and important potential research variables are recognized and controlled.

The article republished here (Lynch CJ. 1969. The so-called Swiss mouse. Lab Anim Care 19: 214–220) describes in detail the origin of the “Swiss” family of interrelated mouse stocks and strains and is written by the person actually responsible for setting in motion the events that led to the availability of these animal models. These include commercial stocks from various vendors that we recognize and use to this day as Swiss-Webster, ICR, and CD-1 along with related inbred strain families such as SWR, NMRI, and even the ever-present FVB mice that exploded into use when it became the background of choice for pronuclear injection for transgenic mouse studies.

Dr. Clara Lynch, BA, PhD (1882 to 1985), was a prominent scientist who is primarily known for studying the impacts of genetics on cancer during a distinguished career at Rockefeller University (and as it was earlier known, the Rockefeller Institute for Medical Research), but she also used cohorts of genetically divergent mice to evaluate the contributions of mouse genes on the pathogenesis of yellow fever and tuberculosis. In the early 1900s, individual research facilities were frequently maintaining their own strains and stocks, and for the work she was doing, it was clear to Dr. Lynch early in her career that some additional breeding stock from an outside population would be very useful. For this reason, she worked to acquire the original Swiss founders and then established breeding colonies at Rockefeller to expand and produce the large groups required for genetic studies. Subsequently, the cooperative aspects of interlaboratory sharing allowed these Swiss-origin mice to serve as seed stock for additional populations maintained at other institutions and by commercial breeders. Specific pathogen-free populations were eventually created as the colony health aspects of modern mouse care became more important.

When this review was published in Laboratory Animal Care it was accompanied by an introduction in the Letters section of that issue, which is included below. Dr. Robert Leader, DVM, MS, was head of the Laboratory of Comparative Pathology at Rockefeller at the time, and he submitted a note regarding Dr. Lynch’s career at that institution and an anecdote relating to the circumstances surrounding the initial acquisition of the founder mice. Many of us have been approached by a graduate student or postdoc asking if they could bring back a few breeders when they visit a collaborator laboratory in a foreign country, and we often must veto those requests and explain the various laws, regulations, and institutional policies governing imports and the various permits that are required. In contrast, things were simpler in 1926, and Dr. Lynch found that she could transport 9 mice on a trans-Atlantic crossing by ship and then have them accepted through US customs! This is a nice complement to the lore of research mouse history that has a place alongside the story of Miss Abbie Lathrop’s fancy mouse care, breeding, and experimentation that contributed to the establishment of the well-known C57/58 family of inbred mice.

I noted 2 things of interest while preparing this article. First, it seems only fitting that a scientist who studied some of the consequences of aging lived to be 103 y old. Second, a group of 9 animals serving as the original imported founders is the same number of animals that some sources list for the initial establishment of the Syrian hamster as a captive research species, and both cases show how a multitude of advances in scientific understanding can be catalyzed by a small number of animals being nurtured and developed as a resource by knowledgeable research personnel.

[From “Letters” in the April 1969 issue of Laboratory Animal Care]

To the Editor:

In the spring of 1918 a young geneticist fresh from the laboratory of Dr. Morgan at Columbia University joined Dr. Murphy’s group at The Rockefeller Institute. That young geneticist was Clara Lynch, who still makes her presence known around the halls of The Rockefeller University with her bright blue eyes and sparkling sense of humor.

It was when she traveled to France on summer vacation during 1926 that she got the idea to obtain from Lausanne the original 7 female and 2 male Swiss mice from which so many millions have since descended to be used in biomedical research. It is a fascinating story that Dr. Lynch tells about the trip back to the U. S. She kept the mice in a pastry box and was assisted by the steward on the ship in daily cleaning of the cage. During the cleaning process, the mice were placed in the wash basin. Dr. Lynch told me with considerable amusement about her arrival at customs. Of course, there were few rules governing the importation of animals at that time, and the extreme curiosity and interest in her mice by the customs inspector was responsible for her getting through customs very quickly. She said, “You see, the mice got me into the U. S. I did not get the mice in.”

When asked which of her scientific accomplishments had given her the greatest thrill, she said it was when she began to inspect some of the mice she had painted with tar in subcarcinogenic levels on various parts of their skin and found that there was an increase in the incidence of pulmonary tumors. Furthermore, the incidence was much greater in certain genetic strains than in others, thus proving experimentally the previous theory that there is indeed genetic predisposition to tumors caused by carcinogens. Her work has added significantly to our understanding of the interplay between heredity and environment as they influence the development of cancer.

It is a joy and a privilege to be a friend of the charming and lovely Dr. Clara Lynch. Her paper, published in this issue of the journal, is an important chronicle in the history of Swiss mice.

R. W. Leader, D.V.M.

The Rockefeller University

New York, N. Y. 10021