The acrosome is a unique organelle that plays an important role at the site of sperm-zona pellucida binding during the fertilization process, and is lost in globozoospermia, an inherited infertility syndrome in humans. Although the acrosome is known to be derived from the Golgi apparatus, molecular mechanisms underlying acrosome formation are largely unknown. Here we show that Golgi-associated PDZ-and coiled-coil motif-containing protein (GOPC), a recently identified Golgi-associated protein, is predominantly localized at the trans-Golgi region in round spermatids, and male mice in which GOPC has been disrupted are infertile with globozoospermia. The primary defect was the fragmentation of acrosomes in early round spermatids, and abnormal vesicles that failed to fuse to developing acrosomes were apparent. In later stages, nuclear malformation and an abnormal arrangement of mitochondria, which are also characteristic features of human globozoospermia, were observed. Interestingly, intracytoplasmic sperm injection (ICSI) of such malformed sperm into oocytes resulted in cleavage into blastocysts only when injected oocytes were activated. Thus, GOPC provides important clues to understanding the mechanisms underlying spermatogenesis, and the GOPC-deficient mouse may be a unique and valuable model for human globozoospermia.

DFN3, an X chromosome-linked nonsyndromic mixed deafness, is caused by mutations in the BRN-4 gene, which encodes a POU transcription factor. Brn-4-deficient mice were created and found to exhibit profound deafness. No gross morphological changes were observed in the conductive ossicles or cochlea, although there was a dramatic reduction in endocochlear potential. Electron microscopy revealed severe ultrastructural alterations in cochlear spiral ligament fibrocytes. The findings suggest that these fibrocytes, which are mesenchymal in origin and for which a role in potassium ion homeostasis has been postulated, may play a critical role in auditory function.

␣1 subunit of the voltage-dependent Ca 2؉ channel is essential for channel function and determines the functional specificity of various channel types. ␣1E subunit was originally identified as a neuron-specific one, but the physiological function of the Ca 2؉ channel containing this subunit (␣1E Ca 2؉ channel) was not clear compared with other types of Ca 2؉ channels because of the limited availability of specific blockers. To clarify the physiological roles of the ␣1E Ca 2؉ channel, we have generated ␣1E mutant (␣1E؊͞؊) mice by gene targeting. The lacZ gene was inserted in-frame and used as a marker for ␣1E subunit expression. ␣1E؊͞؊ mice showed reduced spontaneous locomotor activities and signs of timidness, but other general behaviors were apparently normal. As involvement of ␣1E in pain transmission was suggested by localization analyses with 5-bromo-4-chloro-3-indolyl ␤-D-galactopyranoside staining, we conducted several pain-related behavioral tests using the mutant mice. Although ␣1E؉͞؊ and ␣1E؊͞؊ mice exhibited normal pain behaviors against acute mechanical, thermal, and chemical stimuli, they both showed reduced responses to somatic inflammatory pain. ␣1E؉͞؊ mice showed reduced response to visceral inflammatory pain, whereas ␣1E؊͞؊ mice showed apparently normal response compared with that of wild-type mice. Furthermore, ␣1E؊͞؊ mice that had been presensitized with a visceral noxious conditioning stimulus showed increased responses to a somatic inflammatory pain, in marked contrast with the wild-type mice in which long-lasting effects of descending antinociceptive pathway were predominant. These results suggest that the ␣1E Ca 2 ؉ channel controls pain behaviors by both spinal and supraspinal mechanisms.V oltage-dependent calcium channels (VDCCs) are classified into several distinct groups termed L-, N-, P-, Q-, R-, and T-types (1, 2). These types of VDCCs play important roles in various neuronal activities, including the control of neurotransmitter release, membrane excitability, and gene expression (3), but exact roles of each channel type are not necessarily clarified. In particular, functions of the R-type Ca 2ϩ channel are least understood. The R-type Ca 2ϩ channel was originally defined as a channel ''Resistant'' to blockers for L-, N-, P-, and Q-type Ca 2ϩ channels (4); therefore, it is possible that the R-type current is a mixture of several different drug-resistant Ca 2ϩ currents. Although the R-type Ca 2ϩ channel is suggested to play a critical role in the release of neurotransmitters and somatodendritic excitability in a certain set of neurons (4-6), the physiological functions of this channel remain to be clarified.VDCCs are heteromultimers composed of ␣ 1 , ␣ 2 -␦, ␤, and ␥ subunits. ␣ 1 subunit is essential for channel function and determines the type of each Ca 2ϩ channel. So far, 10 different ␣ 1 cDNAs (␣ 1A-I and ␣ 1S ) have been cloned from a variety of tissues, and extensive studies have been made to clarify the relationship between each cloned ␣ 1 subunit and native Ca 2ϩ channels (2)....

Hereditary deafness affects approximately 1 in 2,000 children. Mutations in the gene encoding the cochlear gap junction protein connexin 26 (CX26) cause prelingual, nonsyndromic deafness and are responsible for as many as 50% of hereditary deafness cases in certain populations. Connexin-associated deafness is thought to be the result of defective development of auditory sensory epithelium due to connexion dysfunction. Surprisingly, CX26 deficiency is not compensated for by the closely related connexin CX30, which is abundantly expressed in the same cochlear cells. Here, using two mouse models of CX26-associated deafness, we demonstrate that disruption of the CX26-dependent gap junction plaque (GJP) is the earliest observable change during embryonic development of mice with connexin-associated deafness. Loss of CX26 resulted in a drastic reduction in the GJP area and protein level and was associated with excessive endocytosis with increased expression of caveolin 1 and caveolin 2. Furthermore, expression of deafness-associated CX26 and CX30 in cell culture resulted in visible disruption of GJPs and loss of function. Our results demonstrate that deafness-associated mutations in CX26 induce the macromolecular degradation of large gap junction complexes accompanied by an increase in caveolar structures.