Mutations in REEP6 Cause Autosomal-Recessive Retinitis Pigmentosa

Retinitis pigmentosa (RP) is the most frequent form of inherited retinal dystrophy. RP is genetically heterogeneous and the genes identified to date encode proteins involved in a wide range of functional pathways, including photoreceptor development, phototransduction, the retinoid cycle, cilia, and outer segment development. Here we report the identification of biallelic mutations in Receptor Expression Enhancer Protein 6 (REEP6) in seven individuals with autosomal-recessive RP from five unrelated families. REEP6 is a member of the REEP/Yop1 family of proteins that influence the structure of the endoplasmic reticulum but is relatively unstudied. The six variants identified include three frameshift variants, two missense variants, and a genomic rearrangement that disrupts exon 1. Human 3D organoid optic cups were used to investigate REEP6 expression and confirmed the expression of a retina-specific isoform REEP6.1, which is specifically affected by one of the frameshift mutations. Expression of the two missense variants (c.383C>T [p.Pro128Leu] and c.404T>C [p.Leu135Pro]) and the REEP6.1 frameshift mutant in cultured cells suggest that these changes destabilize the protein. Furthermore, CRISPR-Cas9-mediated gene editing was used to produce Reep6 knock-in mice with the p.Leu135Pro RP-associated variant identified in one RP-affected individual. The homozygous knock-in mice mimic the clinical phenotypes of RP, including progressive photoreceptor degeneration and dysfunction of the rod photoreceptors. Therefore, our study implicates REEP6 in retinal homeostasis and highlights a pathway previously uncharacterized in retinal dystrophy

BRCA1-mutated and basal-like breast cancers have similar aCGH profiles and a high incidence of protein truncating TP53 mutations

<p>Abstract</p> <p>Background</p> <p>Basal-like breast cancers (BLBC) are aggressive breast cancers for which, so far, no targeted therapy is available because they typically lack expression of hormone receptors and HER2. Phenotypic features of BLBCs, such as clinical presentation and early age of onset, resemble those of breast tumors from <it>BRCA1</it>-mutation carriers. The genomic instability of <it>BRCA1</it>-mutated tumors can be effectively targeted with DNA-damaging agents and poly-(ADP-ribose) polymerase 1 (PARP1) inhibitors. Molecular similarities between BLBCs and <it>BRCA1</it>-mutated tumors may therefore provide predictive markers for therapeutic response of BLBCs.</p> <p>Methods</p> <p>There are several known molecular features characteristic for <it>BRCA1</it>-mutated breast tumors: 1) increased numbers of genomic aberrations, 2) a distinct pattern of genomic aberrations, 3) a high frequency of <it>TP53 </it>mutations and 4) a high incidence of complex, protein-truncating <it>TP53 </it>mutations. We compared the frequency of <it>TP53 </it>mutations and the pattern and amount of genomic aberrations between <it>BRCA1</it>-mutated breast tumors, BLBCs and luminal breast tumors by <it>TP53 </it>gene sequencing and array-based comparative genomics hybridization (aCGH) analysis.</p> <p>Results</p> <p>We found that the high incidence of protein truncating <it>TP53 </it>mutations and the pattern and amount of genomic aberrations specific for BRCA1-mutated breast tumors are also characteristic for BLBCs and different from luminal breast tumors.</p> <p>Conclusions</p> <p>Complex, protein truncating TP53 mutations in BRCA1-mutated tumors may be a direct consequence of genomic instability caused by BRCA1 loss, therefore, the presence of these types of TP53 mutations in sporadic BLBCs might be a hallmark of BRCAness and a potential biomarker for sensitivity to PARP inhibition. Also, our data suggest that a small subset of genomic regions may be used to identify BRCA1-like BLBCs. BLBCs share molecular features that were previously found to be specific for BRCA1-mutated breast tumors. These features might be useful for the identification of tumors with increased sensitivity to (high-dose or dose-dense) alkylating agents and PARP inhibitors.</p

Biallelic Mutation of ARHGEF18, Involved in the Determination of Epithelial Apicobasal Polarity, Causes Adult-Onset Retinal Degeneration

Mutations in more than 250 genes are implicated in inherited retinal dystrophy; the encoded proteins are involved in a broad spectrum of pathways. The presence of unsolved families after highly parallel sequencing strategies suggests that further genes remain to be identified. Whole-exome and -genome sequencing studies employed here in large cohorts of affected individuals revealed biallelic mutations in ARHGEF18 in three such individuals. ARHGEF18 encodes ARHGEF18, a guanine nucleotide exchange factor that activates RHOA, a small GTPase protein that is a key component of tight junctions and adherens junctions. This biological pathway is known to be important for retinal development and function, as mutation of CRB1, encoding another component, causes retinal dystrophy. The retinal structure in individuals with ARHGEF18 mutations resembled that seen in subjects with CRB1 mutations. Five mutations were found on six alleles in the three individuals: c.808A>G (p.Thr270Ala), c.1617+5G>A (p.Asp540Glyfs∗63), c.1996C>T (p.Arg666∗), c.2632G>T (p.Glu878∗), and c.2738_2761del (p.Arg913_Glu920del). Functional tests suggest that each disease genotype might retain some ARHGEF18 activity, such that the phenotype described here is not the consequence of nullizygosity. In particular, the p.Thr270Ala missense variant affects a highly conserved residue in the DBL homology domain, which is required for the interaction and activation of RHOA. Previously, knock-out of Arhgef18 in the medaka fish has been shown to cause larval lethality which is preceded by retinal defects that resemble those seen in zebrafish Crumbs complex knock-outs. The findings described here emphasize the peculiar sensitivity of the retina to perturbations of this pathway, which is highlighted as a target for potential therapeutic strategies

Abstracts from the 8th International Conference on cGMP Generators, Effectors and Therapeutic Implications

This work was supported by a restricted research grant of Bayer AG

Losdolobus xaruanus Lise & Almeida, 2006, n. sp.

&lt;i&gt;Losdolobus xaruanus&lt;/i&gt; n. sp. &lt;p&gt;Figs 1&ndash;18&lt;/p&gt; &lt;p&gt; &lt;b&gt;Types.&lt;/b&gt; Male holotype and female allotype from Palmas, Bag&eacute;, Rio Grande do Sul, Brazil, Luciano Almeida leg., deposited in MCTP 17.550 and MCTP 17.551, respectively.&lt;/p&gt; &lt;p&gt; &lt;b&gt;Etymology.&lt;/b&gt; The specific name is a Latinized adjective taken from the Brazilian Xarrua Indians that were the earlier inhabitant of the area.&lt;/p&gt; &lt;p&gt; &lt;b&gt;Diagnosis.&lt;/b&gt; This species is similar to &lt;i&gt;L. ybypora.&lt;/i&gt; The males can be differentiated of it by the presence of an elongated tibia of palpus and filiform embolus. Females with non conspicuous secretory glands on the genitalia, by shape of the epigynum and by a not inflated tibia of the palpus and by the presence of a very narrowed rod.&lt;/p&gt; &lt;p&gt; &lt;b&gt;Description.&lt;/b&gt; Male (holotype). Conditions. missing right leg IV. Carapace, labium, endites and sternum yellow. Chelicerae yellow, fang fulvous with some bristles on the anterior face and long ones on the apical promargin. Legs yellow. Abdomen yellow with dusky almost circular spots of different sizes on dorsum and laterals (Figs 1, 3), venter yellow (Fig. 2). Spinnerets yellow, bristly.&lt;/p&gt; &lt;p&gt;Total length 2.60. Carapace oval, 1.00 long, 0.84 wide, 0.40 high (Fig. 1) Chelicerae 0.40 long, 0.20 wide. Clypeus 0.06 high. Labium triangular, 0.16 long, 0.16 wide. Endites 0.34 long, 0.14 wide at the apical third. transversely excavated, bristly. Sternum 0.60 long, 0.60 wide, not produced anteriorly, truncated posteriorly, marginated by a narrow fulvous band, with precoxal triangles on each leg (Fig. 2). Legs yellow with long slender dark bristles. Abdomen (Figs 1&ndash;3), 1.50 long, 1.00 wide, 1.00 high. Eyes pearly white, surrounded with black. Eye diameter and interdistances ALE 0.08 long, 0.07 wide, PME 0.08 long, 0.05 wide, PLE 0.09 long, 0.08 wide, PME&ndash;PME 0,0 4, PME&ndash;PLE 0.07, PME &ndash;ALE 0.04, PLE&ndash;PLE 0.26, ALE&ndash;PLE touching. Leg spination. III femur 1v apical; tibia d0&shy;1&shy;0; r0&shy;0&shy;.1; v0&shy;0&shy;2; metatarsus p1&shy;0&shy;1, r1&shy;0.1; IV f&ecirc;mur p1 apical; t&iacute;bia p1&shy;1&shy;1&shy;; r0&shy;0&shy; 1; metatarsus p1&shy;1&shy;1&shy;; r1&shy;0&shy;1; v2 &shy;0&shy;2. Leg measurements I femur 1.10/patella 0,50/tibia 1.00/metatarsus 0.98/tarsus 0.46/total 4.04; II 1.10/0.50/1.00/1.00/0.46/4.06; III 0.86/0.40/ 0.74/0.80 /0.36 /3.16; IV 1.24/0.42/1.10 / 1.24 /0.40/4.40. Palpus femur 0.64 long, 0.14 wide, patella 0.30 long, 0.14 wide, tibia 0.56 long, 0.16 wide, cymbium 0.50 long, 0.08 wide, bulb plus embolus 0.56 long, 0.20 wide. Palpal bulb longer than wide, simple with long and acuminate embolus and sinuous reservoir (Figs 5&ndash;7).&lt;/p&gt; &lt;p&gt;Female (allotype). Conditions. right leg II missing from patella to tarsus; left leg II only has atrophied coxa and trochanter; from right leg I and III it was removed tibia, metatarsus and tarsus for SEM purposes. Carapace, chelicerae, labium, sternum and endites yellow. Abdomen yellow grayish without the gray spots observed on the male. Spinnerets yellow.&lt;/p&gt; &lt;p&gt;Total length 2.90. Carapace 1.20 long, 0.88 wide, 0.44 high. Abdomen 1.66 long, 1.20 wide, 1.20 high. Eye diameters and interdistances ALE 0.09 long, 0.05 wide, PME 0.09 long, 0.07 wide, PLE 0.08 long, 0,0 7 wide, PME&ndash;PME 0.02, PME&ndash;PLE 0.07,PME&ndash;ALE 0.02, PLE&ndash;PLE 0.28. Chelicerae 0.50 long, 0.20 wide. Labium 0.16 long, 0.24 wide. Endites 0.34 long, 0.16 wide. Sternum as long as wide, 0.60. Leg spination: I femur d1 median, tibia v1; III tibia d1 median, p1.1, r1.1, v2.2; metatarsus p1.1, v2.2; IV tibia p1.1, r1.1, v2.1.1.2; metatarsus p1.1.1, r1.0.1, v1.1.2. Leg measurements I femur 1.04/patella 0.50/tibia 0.86/metatarsus 0.90/tarsus 0.36/total 3.66; II femur 1.00; III. 0.84/0.40/ 0.64/ 0.80/0.30/2.98; IV 1.20/0.46/0.94/1.12/0.40/4.12. Tarsal organ (Figs15&ndash;16) with three short central receptor lobes and six very long and acuminate cuticular ones. Claws long with few long teeth on the lateral flange. Claw tuffs constituted by different types of bristles and hairs (Figs 13&ndash;15). On top of tarsus, above the claws, there are two long curve chaetae pointed forward, ventrally two more, shorter than the dorsal ones (Fig. 13). Bothrium smooth with elliptical tricheme aperture and transversely depressed forming two widely spaced transverse ridges. Trichobothriae typical for family (Fig. 18). Proprioreceptors bristle plumose (Figs 11&ndash;17). Gland pore plate as in figure 12. Palpal tibia not dilated (Fig. 8). Internal genitalia as in (Fig. 10).&lt;/p&gt; &lt;p&gt; &lt;b&gt;Distribution.&lt;/b&gt; Known only from the type locality.&lt;/p&gt;Published as part of &lt;i&gt;Lise, Arno A. &amp; Almeida, Luciano, 2006, A new species of Losdolobus Platnick &amp; Brescovit, 1994 (Araneae: Dysderoidea: Orsolobidae) from southern Brazil, pp. 23-27 in Zootaxa 1277&lt;/i&gt; on pages 24-27, DOI: &lt;a href="http://zenodo.org/record/273500"&gt;10.5281/zenodo.273500&lt;/a&gt

FIGURES 1 – 10. Losdolobus xaruanus n in A new species of Losdolobus Platnick & Brescovit, 1994 (Araneae: Dysderoidea: Orsolobidae) from southern Brazil

FIGURES 1 – 10. Losdolobus xaruanus n. sp. 1 – 7 male. 1 – 3 habitus (1 dorsal, 2 ventral, 3 lateral); 4 carapace and chelicerae, frontal; 5 – 7 palpus (5 prolateral, 6 retrolateral, 7 ventral); 9 – 10 female genitalia (9 ventral, 10 dorsal)