Pelger-Huet Anomaly
In Australian Shepherd Dogs
What is Pelger-Huet Anomaly?
It should not be confused with pseudo-Pelger-Huet Anomaly, which can result from myeloid leukemia, myelodysplasia, and bi-lineage acute lymphocytic leukemia, after considerable chemotherapy treatments, as well as certain deficiencies or excesses of substances. It is not a heritable disease, but appears very similar to the true Pelger-Huet Anomaly.
What Causes Pelger-Huet Anomaly?
It is similar to the double merle gene in Australian Shepherds in its lethal form, and is thought to have developed because genes have been inadvertently concentrated due to selective breeding.
Cellular Structure
The gene responsible for the Pelger-Huet anomaly is the LBR (Lamin B receptors) gene on subband 1q42.1, first discovered in crossbreeding experiments with rabbits in Germany. The gene product of LBR is responsible for maintaining nuclear membrane structure. Homozygous dominant individuals have very coarsely and tightly bound neutrophils that are typically not capable of normal function. Heterozygous individuals have neutrophils with lobed, dumbell shaped nuclei, also called "pince-nez" because of their similarity to pinched nose spectacles.
LBR interacts with the heterochromatin proteins, which is thought to be the cause for the excessive clumping of chromatin observed. These abnormalities in heterozygous individuals do not seem to effect neutrophil function and the cells can phagocytize normally. Homozygous individuals are very rare, but when they do occur, have neutrophils that are a single round shape with eccentric nuclei, clumped chromatin, and and little to no segmentation.
Homozygous vs. Heterozygous Individuals
In the very rare case that a homozygous individual does survive past puppyhood, it is susceptible to skeletal anomalies, developmental delays, and seizures.
Discussion Point...
Is it ethical or worthwhile to breed to another heterozygous female carrier who was equally prestigious in her awards and accomplishments, if her owner approached you and asked if you would allow a breeding to your sire?
References...
Australian Shepherd Club. "Homozygous "Lethal White" Merles." Lethal White Double Merle. ASL, n.d. Web. 04 May 2013.
Bethurum, Pam. "Australian Shepherd Club of America, Inc. | White Deafness." Australian Shepherd Club of America, Inc. | White Deafness. ASCA, 2009. Web. 04 May 2013.
Cloyd, Mark. "Australian Shepherd Health Concerns, Required Dysplasia Testing, DNA Tests - Pure Stock Aussies." Australian Shepherd Health Concerns, Required Dysplasia Testing, DNA Tests - Pure Stock Aussies. Pure Stock Aussies, n.d. Web. 04 May 2013.
Constantino, Benie T. "Pelger-Huët Anomaly—Morphology, Mechanism, and Significance in the Peripheral Blood Film." Labmedicine. CML Healthcare, 27 Aug. 2004. Web.
DOG DNA. "Australian Shepherd." Dog DNA Breed Testing. Innersanctum, 2013. Web. 04 May 2013.
Kanwar, Vikramjit S. "Pelger-Huet Anomaly ." Pelger-Huet Anomaly. Medscape, 2013. Web. 04 May 2013.
Ogushi, Kara. "HOW TO Manage Your Dog’s Pelger-Huët Anomaly." HOW TO Manage Your Dog's Pelger-Huët Anomaly. Find A Vet, n.d. Web. 04 May 2013.
Sharp, C.A. "Australian Shepherd Health & Genetics Institute, Inc." Australian Shepherd Health & Genetics Institute, Inc. Australian Shepherd Health & Genetics Institute, Inc, n.d. Web. 04 May 2013.
Sharp, C.A. "Australian Shepherd Health & Genetics Institute, Inc." Australian Shepherd Health & Genetics Institute, Inc. Double Helix Network News, 2007. Web. 04 May 2013.