Correlation Between Daam2 Expression Changes and Demyelination in Guillain-Barre Syndrome

Formins in Human Disease

Almost 25 years have passed since a mutation of a formin gene, DIAPH1, was identified as being responsible for a human inherited disorder: a form of sensorineural hearing loss. Since then, our knowledge of the links between formins and disease has deepened considerably. Mutations of DIAPH1 and six other formin genes (DAAM2, DIAPH2, DIAPH3, FMN2, INF2 and FHOD3) have been identified as the genetic cause of a variety of inherited human disorders, including intellectual disability, renal disease, peripheral neuropathy, thrombocytopenia, primary ovarian insufficiency, hearing loss and cardiomyopathy. In addition, alterations in formin genes have been associated with a variety of pathological conditions, including developmental defects affecting the heart, nervous system and kidney, aging-related diseases, and cancer. This review summarizes the most recent discoveries about the involvement of formin alterations in monogenic disorders and other human pathological conditions, especially cancer, with which they have been associated. In vitro results and experiments in modified animal models are discussed. Finally, we outline the directions for future research in this field.

Increased dishevelled associated activator of morphogenesis 2, a new podocyte-associated protein, in diabetic nephropathy

BACKGROUND

Previously, by using proteomic analysis and RNA sequencing in isolated glomeruli, we identified several novel differentially expressed proteins in human and mouse diabetic nephropathy (DN) versus controls, including dishevelled associated activator of morphogenesis 2 (DAAM2). DAAM2 binds the Wnt effector Dvl. We aimed to study possible contributions of DAAM2 to DN.

METHODS

We assessed DAAM2 by immunostaining in non-cancer regions of human nephrectomy (Nx), DN and normal donor kidney tissues. We also examined DAAM2 in DN mice (db/db eNOS-/-) and Nx mice. DN mice treated with angiotensin-converting enzyme inhibitor (ACEI), dipeptidyl peptidase 4 inhibitor (DPP4I) or vehicle were compared. DAAM2 was knocked down in primary cultured podocytes by small interfering RNA to study its effects on cell function.

RESULTS

In normal human glomeruli, DAAM2 was expressed only on podocytes. DAAM2 expression was increased in both Nx and DN versus normal donors. Podocyte DAAM2 expression was increased in DN and Nx mouse models. Glomerular DAAM2 expression correlated with glomerular size and was decreased significantly by ACEI while DPP4I only numerically reduced DAAM2. In primary cultured podocytes, knockdown of DAAM2 enhanced adhesion, slowed migration, activated Wnt-β-catenin signaling and downregulated mammalian target of rapamycin complex 1 (mTORC1) and Rho activity.

CONCLUSIONS

Podocyte DAAM2 is upregulated in both Nx and DN, which could be contributed to by glomerular hypertrophy. We hypothesize that DAAM2 regulates podocyte function through the mTORC1, Wnt/β-catenin and Rho signaling pathways.

iPSCs from people with MS can differentiate into oligodendrocytes in a homeostatic but not an inflammatory milieu

Multiple sclerosis (MS) is an inflammatory and demyelinating disease of the central nervous system (CNS) that results in variable severities of neurodegeneration. The understanding of MS has been limited by the inaccessibility of the affected cells and the lengthy timeframe of disease development. However, recent advances in stem cell technology have facilitated the bypassing of some of these challenges. Towards gaining a greater understanding of the innate potential of stem cells from people with varying degrees of disability, we generated induced pluripotent stem cells (iPSCs) from peripheral blood mononuclear cells derived from stable and progressive MS patients, and then further differentiated them into oligodendrocyte (OL) lineage cells. We analyzed differentiation under both homeostatic and inflammatory conditions via sustained exposure to low-dose interferon gamma (IFNγ), a prominent cytokine in MS. We found that all iPSC lines differentiated into mature myelinating OLs, but chronic exposure to IFNγ dramatically inhibited differentiation in both MS groups, particularly if exposure was initiated during the pre-progenitor stage. Low-dose IFNγ was not toxic but led to an early upregulation of interferon response genes in OPCs followed by an apparent redirection in lineage commitment from OL to a neuron-like phenotype in a significant portion of the treated cells. Our results reveal that a chronic low-grade inflammatory environment may have profound effects on the efficacy of regenerative therapies.

The dynamic expression of canonical Wnt/β-catenin signalling pathway in the pathologic process of experimental autoimmune neuritis

Background: Guillain-Barré syndrome (GBS), an autoimmune disease and an acute inflammation disorder, is currently the most frequent cause of acute flaccid paralysis worldwide. EAN, an animal model of GBS, is a CD4+ T cell-mediated autoimmune disease of the PNS. Wnt/β-catenin signals are critically important to several fundamental aspects of peripheral nerve development and play a crucial role in Schwann cell proliferation. Here, we investigate the role of Wnt/β-catenin signalling cascades in EAN rats.Methods: 28 male Lewis rats weighing 170 ± 10 g were randomly divided into control group (n = 7) and EAN groups (Early group; Peak group and Recovery group. n = 7 per group). EAN rats were immunized with P2_57-81 peptide; weighed daily, and the neurologic signs of EAN were evaluated every day. The sciatic nerve was taken on the days 10, 17, and 30 p.i. for H&E staining, transmission electron microscopy and immunohistochemical staining; blood samples were collected weekly from caudal vein to detect IFN-γ, IL-4, TGF-β1; and the sciatic nerve was taken to examinate the dynamics expression of Wnt/β-catenin pathway molecules.Results: In our study, we chose tail-root injection to better model GBS. Moreover, we observed that IFN-γ levels paralleled clinical EAN, and the levels of TGF-β1 and IL-4 gradually increased and peaked in the recovery phase. In addition, we have shown that canonical Wnt signalling is upregulated and reached a peak in the late recovery phase.Conclusion: Our findings suggest that Wnt/β-catenin signalling is associated with the promotion of remyelination in EAN rats.

Whole exome sequencing identifies a rare variant in DAAM2 as a potential candidate in idiopathic pulmonary ossification

Background

Diffuse pulmonary ossification (DPO) is a rare disease characterized by bone tissue formation in the lung. DPO can be classified into idiopathic pulmonary ossification (IPO) and secondary pulmonary ossification. Cases with no identified etiology are classified as IPO. Variants of dishevelled associated activator of morphogenesis 2 (DAAM2) have been reported to be involved in the bone-resorption of osteoclasts.

Methods

Whole exome sequencing (WES) was used on samples from a patient with IPO and his healthy parents. The effects of all variants were determined using functional predictors (PolyPhen-2, SIFT, FATHMM and MutationTaster); variants existing only in the patient were further screened compared with his healthy parents.

Results

Forty deleterious variants, including 25 single nucleotide variants (SNVs) and 15 insertions and deletions (indels), were identified by WES. Finally, DAAM2 (c.G2960T:p.R987L) was screened by pathway analysis.

Conclusions

We identified a novel variant of DAAM2 (c.G2960T:p.R987L) that might participate in the disease process of IPO.

ADNP differentially interact with genes/proteins in correlation with aging: a novel marker for muscle aging

Activity-dependent neuroprotective protein (ADNP) is essential for embryonic development with ADNP mutations leading to syndromic autism, coupled with intellectual disabilities and motor developmental delays. Here, mining human muscle gene-expression databases, we have investigated the association of ADNP transcripts with muscle aging. We discovered increased ADNP and its paralogue ADNP2 expression in the vastus lateralis muscle of aged compared to young subjects, as well as altered expression of the ADNP and the ADNP2 genes in bicep brachii muscle of elderly people, in a sex-dependent manner. Prolonged exercise resulted in decreased ADNP expression, and increased ADNP2 expression in an age-dependent manner in the vastus lateralis muscle. ADNP expression level was further correlated with 49 genes showing age-dependent changes in muscle transcript expression. A high degree of correlation with ADNP was discovered for 24 genes with the leading gene/protein being NMNAT1 (nicotinamide nucleotide adenylyl transferase 1). Looking at correlations differentiating the young and the old muscles and comparing protein interactions revealed an association of ADNP with the cell division cycle 5-like protein (CDC5L), and an aging-muscle-related interactive pathway in the vastus lateralis. In the bicep brachii, very high correlation was detected with genes associated with immune functions as well as mitochondrial structure and function among others. Taken together, the results suggest a direct association of ADNP with muscle strength and implicate ADNP fortification in the protection against age-associated muscle wasting.