We have identified a mouse recessive mutation that leads to attenuated and hyperpermeable retinal vessels, recapitulating some pathological features of familial exudative vitreoretinopathy (FEVR) in human patients. DNA sequencing reveals a single nucleotide insertion in the gene encoding the low-density lipoprotein receptor-related protein 5 (LRP5), causing a frame shift and resulting in the replacement of the C-terminal 39 amino acid residues by 20 new amino acids. This change eliminates the last three PPP(S/T)P repeats in the LRP5 cytoplasmic domain that are important for mediating Wnt/beta-catenin signaling. Thus, mutant LRP5 protein is probably unable to mediate its downstream signaling. Immunostaining and three-dimensional reconstructions of retinal vasculature confirm attenuated retinal vessels. Ultrastructural data further reveal that some capillaries lack lumen structure in the mutant retina. We have also verified that LRP5 null mice develop similar alterations in the retinal vasculature. This study provides direct evidence that LRP5 is essential for the development of retinal vasculature, and suggests a novel role played by LRP5 in capillary maturation. LRP5 mutant mice can be a useful model to explore the clinical manifestations of FEVR.

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Purpose: To investigate the morphological features of nonpuerperal mastitis on magnetic resonance imaging (MRI). Materials and Methods:MRI results of 27 patients diagnosed with nonpuerperal mastitis were retrospectively analyzed according to the Breast Imaging Reporting and Data System (BI-RADS).Results: According to the enhanced MRI results, 22 cases presented as nonmass-like enhancements and five cases presented as masses. For the 22 nonmass-like enhancement lesions, one case showed as a homogeneous enhancement and 21 cases showed as heterogeneous enhancements. In the 21 heterogeneous enhancement cases, 13 contained lesions of rim-like enhancement. With regard to the number of lesions with rim-like enhancement, 11 presented as multiple and two as single. In the five mass lesions, three presented as rim enhancements. Indications of rim or rim-like enhancement accounted for 59% (16/27) of all cases. For the 16 cases that presented with signs of rim or rim-like enhancement, the central hypointensity area surrounded by enhanced rim or rim-like entity showed as hyperintensity in 14 cases and hypointensity or heterointensity in two cases on T2-weighted imaging.Conclusion: On contrast-enhanced MRI, most nonpuerperal mastitis presented as nonmass-like lesion with heterogeneous signal intensity. The observation of signs of rim or rim-like enhancement on contrast-enhanced MRI with central hypointensity areas showing as hyperintensity on T2-weighted imaging is suggestive of the possibility of nonpuerperal mastitis. MASTITIS MOST COMMONLY OCCURS in lactating females when bacteria enter through cracks in the nipples (1). Nonpuerperal mastitis is a heterogeneous entity and includes a wide spectrum of disorders such as newborn mastitis, thelitis, bacterial infection of the milk ducts with subsequent abscess or fistula formation, and plasma cell mastitis or granulomatous mastitis, which are nonbacterial infections that generally originate from deeper milk ducts (2). Currently, the rate of benign inflammation in nonlactating breasts is increasing (3). Mammographically, nonpuerperal mastitis often presents with nonspecific imaging features as a focal or diffuse asymmetric density (4,5). Sonographically, it can manifest as a hypoechoic mass (4,5), cyst, or abscess (1,6).Magnetic resonance mammography (MRM) is a wellestablished method to diagnose invasive breast carcinoma and breast carcinoma in situ (7,8). Despite the use of MRM for diagnosis, limited data exist on the characteristics of inflammatory breast diseases on MRM (9). Sporadic reports indicated that breast inflammation might present as mass or nonmass-like enhancement with different distributions and internal enhancement patterns on enhanced MRM, which makes the identification of the disease difficult on MRM. The purpose of this study was to elucidate and define the appearance of nonpuerperal mastitis using a sample of 27 patients. MATERIALS AND METHODS Patient SelectionFrom July 2007 to January 2010, 27 patients diagnosed with mastitis underwent contrast materialenhan...