The Buschke-Ollendorff syndrome: a case report of simultaneous osteo-cutaneous malformations in the hand

The Diverse Cellular Functions of Inner Nuclear Membrane Proteins

The nuclear compartment is delimited by a specialized expanded sheet of the endoplasmic reticulum (ER) known as the nuclear envelope (NE). Compared to the outer nuclear membrane and the contiguous peripheral ER, the inner nuclear membrane (INM) houses a unique set of transmembrane proteins that serve a staggering range of functions. Many of these functions reflect the exceptional position of INM proteins at the membrane-chromatin interface. Recent research revealed that numerous INM proteins perform crucial roles in chromatin organization, regulation of gene expression, genome stability, and mediation of signaling pathways into the nucleus. Other INM proteins establish mechanical links between chromatin and the cytoskeleton, help NE remodeling, or contribute to the surveillance of NE integrity and homeostasis. As INM proteins continue to gain prominence, we review these advancements and give an overview on the functional versatility of the INM proteome.

Modeling-based bone formation transforms trabeculae to cortical bone in the sclerotic areas in Buschke-Ollendorff syndrome. A case study of two females with LEMD3 variants

Buschke-Ollendorff syndrome is a rare autosomal dominant condition caused by pathogenic variants in LEMD3 and characterized by connective tissue nevi and sclerotic bone abnormalities known as osteopoikilosis. The bone phenotype in Buschke-Ollendorff syndrome including osteopoikilosis remains unclear. We investigated bone turnover markers, pelvis and crura X-rays; lumbar spine and femoral neck DXA; bone activity by NaF-PET/CT, bone structure by μCT and dynamic histomorphometry in adults with Buschke-Ollendorff syndrome. Two women aged 25 and 47 years with a BMI of 30 and 32 kg/m², respectively, were included in the investigation. Bone turnover markers were within normal range. aBMD Z-scores were comparable to that of controls in the lumbar spine and increased at the hip. Radiographies exposed spotted areas in crura and pelvis, and NaF-PET/CT exposed abnormal pattern of irregular shaped NaF uptake in the entire skeleton. In both biopsies, μCT showed trabecular structure comparable to that of controls with stellate shaped sclerotic noduli within the cavity and on the endocortex. Histomorphometric analyses of the sclerotic lesions revealed compact lamellar bone with a normal bone remodeling rate, but partly replaced by modeling-based bone formation. Woven bone was not observed in the nodules. Therefore, while bone turnover and BMD were largely within normal reference range in patients with the Buschke-Ollendorff syndrome, osteosclerotic lesions appear to emerge due to modeling-based bone formation with secondary bone remodeling. These observations indicate that LEMD3 may be important for the activation of bone lining cells leading to modeling-based bone formation.

Hamartomas of skin and soft tissue

Hamartomas are benign lesions composed of aberrant disorganized growth of mature tissues. Choristomas are similar, except that they are composed of tissues not normally found at the anatomic site in which the lesion is arising. A wide range of hamartomas and choristomas can arise in the skin and soft tissue. Some of these may cause diagnostic difficulty and potentially be mistaken for neoplasms. Some neoplasms may resemble hamaratomas. Here we review the current clinical and pathologic features of these lesions, both common and rare, and discuss how to distinguish them from other entities in the differential diagnosis.

Nuclear envelopathies: a complex LINC between nuclear envelope and pathology

Since the identification of the first disease causing mutation in the gene coding for emerin, a transmembrane protein of the inner nuclear membrane, hundreds of mutations and variants have been found in genes encoding for nuclear envelope components. These proteins can be part of the inner nuclear membrane (INM), such as emerin or SUN proteins, outer nuclear membrane (ONM), such as Nesprins, or the nuclear lamina, such as lamins A and C. However, they physically interact with each other to insure the nuclear envelope integrity and mediate the interactions of the nuclear envelope with both the genome, on the inner side, and the cytoskeleton, on the outer side. The core of this complex, called LINC (LInker of Nucleoskeleton to Cytoskeleton) is composed of KASH and SUN homology domain proteins. SUN proteins are INM proteins which interact with lamins by their N-terminal domain and with the KASH domain of nesprins located in the ONM by their C-terminal domain.Although most of these proteins are ubiquitously expressed, their mutations have been associated with a large number of clinically unrelated pathologies affecting specific tissues. Moreover, variants in SUN proteins have been found to modulate the severity of diseases induced by mutations in other LINC components or interactors. For these reasons, the diagnosis and the identification of the molecular explanation of "nuclear envelopathies" is currently challenging.The aim of this review is to summarize the human diseases caused by mutations in genes coding for INM proteins, nuclear lamina, and ONM proteins, and to discuss their potential physiopathological mechanisms that could explain the large spectrum of observed symptoms.