Degenerative phenotypes caused by the combined deficiency of murine HIP1 and HIP1r are rescued by human HIP1.
The members of the huntingtin-interacting protein-1 (HIP1) family, HIP1 and HIP1-related (HIP1r), are multi-domain proteins that interact with inositol lipids, clathrin and actin. HIP1 is over-expressed in a variety of cancers and both HIP1 and HIP1r prolong the half-life of multiple growth factor receptors. To better understand the physiological importance of the HIP1 family in vivo, we have analyzed a large cohort of double Hip1/Hip1r knockout (DKO) mice. All DKO mice were dwarfed, afflicted with severe vertebral defects and died in early adulthood. These phenotypes were not observed during early adulthood in the single Hip1 or Hip1r knockouts, indicating that HIP1 and HIP1r compensate for one another. Despite the ability of HIP1 and HIP1r to modulate growth factor receptor levels when over-expressed, studies herein using DKO fibroblasts indicate that the HIP1 family is not necessary for endocytosis but is necessary for the maintenance of diverse adult tissues in vivo. To test if human HIP1 can function similar to mouse HIP1, transgenic mice with 'ubiquitous' expression of the human HIP1 cDNA were generated and crossed with DKO mice. Strikingly, the compound human HIP1 transgenic DKO mice were completely free from dwarfism and spinal defects. This successful rescue demonstrates that the human HIP1 protein shares some interchangeable functions with both HIP1 and HIP1r in vivo. In addition, we conclude that the degenerative phenotypes seen in the DKO mice are due mainly to HIP1 and HIP1r protein deficiency rather than altered expression of neighboring genes or disrupted intronic elements.
Bradley
Sarah V
SV
Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI 48109-0942, USA.
Hyun
Teresa S
TS
Oravecz-Wilson
Katherine I
KI
Li
Lina
L
Waldorff
Erik I
EI
Ermilov
Alexander N
AN
Goldstein
Steven A
SA
Zhang
Claire X
CX
Drubin
David G
DG
Varela
Kate
K
Parlow
Al
A
Dlugosz
Andrzej A
AA
Ross
Theodora S
TS
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics* / Q000502:physiology; D005804:Genes, Lethal; D006801:Humans; D007438:Introns; D007738:Kyphosis / Q000235:genetics; D008141:Lordosis / Q000235:genetics*; D051379:Mice; D018345:Mice, Knockout; D008840:Microfilament Proteins; D010641:Phenotype; D015431:Weight Loss / Q000235:genetics*
D048868:Adaptor Proteins, Signal Transducing; D004268:DNA-Binding Proteins; C073368:HIP1 protein, human; C489536:Hip1 protein, mouse; C489534:Hip1r protein, mouse; D008840:Microfilament Proteins