Science - USA (2021-11-12)

that promoted expression ofIL17A, a pro-
inflammatory cytokine involved in autoimmune
diseases ( 21 ). In animal models of neurodege-
nerative disease, TH17 cells play a direct role in
neuronal loss ( 31 , 32 ). Moreover, human TH 17
cells have been shown to promote blood-brain
barrier disruption and central nervous system
inflammation via IL-17A ( 33 ). Thus, our study
provides a mechanism for TH17 cell–mediated
dopaminergic cell death through secretion of
inflammatory IL-17A, thereby implicating auto-
immunity in LBD (fig. S12).

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ACKNOWLEDGMENTS
We thank the clinical staffs of the Stanford and University of
California San Diego Alzheimer’s Disease Research Centers for
their assistance acquiring patient samples.Funding:This work
was supported by a National Institute of Neurologic Disease and
Stroke K99/R00 Pathway to Independence Award (NS112458-
01A1) (D.G.); an Irene Diamond Fund/AFAR Postdoctoral Transition
Award in Aging (D.G.); a National Institutes of Health National
Institute on Aging (NIA) F32 Fellowship (AG055255-01A1) (D.G.);
the FFG Momentia Project 867741 (L.A.); Austrian Science Fund
(FWF) Project P 31362- B34 (L.A.); FFG Project 867741 PMU FFF
E-20/32/169-UNG (L.A.); the Howard Hughes Medical Institute
(M.M.D.); NIH U19 AG065156, R01 NS115114, P30 AG066515,
and P50 NS062684 (K.L.P.); Michael J. Fox Foundation for
Parkinson’s Research Grants 020756, 16921, and 18411 (K.L.P.);
the Lewy Body Dementia Association (K.L.P.); Alzheimer’s Drug
Discovery Foundation (K.L.P); Sanofi US Services, Inc. (K.L.P.); the
Cure Alzheimer’s Fund (T.W-C.); the NOMIS Foundation (T.W.-C.);
NIA R01 AG045034 05 (T.W-C.); and the NIA-funded Stanford
Alzheimer’s Disease Research Center P50AG047366 (V.W.H.).
Author contributions:D.G. designed experiments and prepared

the manuscript. D.G. conducted confocal microscopy, flow

cytometry, and scRNAseq and scTCRseq. E.T., O.L., A.Y., T.F., A.K.,

and H.O. assisted with sequencing analysis. T.N. performed ex vivo

a-synuclein stimulation experiments. M.S. assisted with clinical

data analysis. D.C. performed sample processing of CSF and blood

cells. K.S., M.S.U., and L.A. performed histology and analysis of

Thy1-aSyn mice. V.W.H., D.R.G., M.M.D., and K.L.P. provided

patient samples and assisted with study design. D.G. and T.W.-C.

wrote and edited the manuscript. All authors read and approved

the final manuscript.Competing interests:K.L.P. has stock

options and has received paid consulting fees from CuraSen

Therapeutics, Inc.Data and materials availability: The scRNAseq

datasets analyzed during the current study are available in the

Gene Expression Omnibus repository under accession numbers

GSE141578 and GSE161192.

SUPPLEMENTARY MATERIALS

science.org/doi/10.1126/science.abf7266

Materials and Methods

Figs. S1 to S12

Table S1

References ( 34 – 39 )

MDAR Reproducibility Checklist

Data S1 to S4

16 November 2020; resubmitted 1 July 2021

Accepted 20 September 2021

Published online 14 October 2021

10.1126/science.abf7266

REPORTS

◥

DEVELOPMENTAL BIOLOGY

Symmetry breaking in the female germline cyst

D. Nashchekin^1 *, L. Busby^1 , M. Jakobs^2 , I. Squires^1 , D. St. Johnston^1 *

In mammals and flies, only one cell in a multicellular female germline cyst becomes an oocyte, but how

symmetry is broken to select the oocyte is unknown. Here, we show that the microtubule (MT) minus

end-stabilizing protein Patronin/CAMSAP marks the futureDrosophilaoocyte and is required for oocyte

specification. The spectraplakin Shot recruits Patronin to the fusome, a branched structure extending into

all cyst cells. Patronin stabilizes more MTs in the cell with the most fusome material. Our data suggest that

this weak asymmetry is amplified by Dynein-dependent transport of Patronin-stabilized MTs. This forms a

polarized MT network, along which Dynein transports oocyte determinants into the presumptive oocyte. Thus,

Patronin amplifies a weak fusome anisotropy to break symmetry and select one cell to become the oocyte.

I

n many organisms, not all female germ

cells develop into oocytes. Some cells be-

come accessory cells that contribute mate-

rial to the oocyte ( 1 ). Mouse female germ

cells form cysts of up to 30 cells, but most

cells undergo apoptosis after transferring cyto-

plasm and centrosomes to the small number

of cells that become oocytes ( 2 , 3 ). InDrosophila,

germline cyst formation starts in the germar-

ium, which has three regions. A stem cell pro-

duces a cystoblast, which then divides four

times with incomplete cytokinesis to generate

a cyst of 16 germ cells connected by intercel-

lular bridges, or“ring canals”( 4 , 5 ). As the cyst

moves through regions 2a and 2b of the ger-

marium, it is surrounded by epithelial follicle

cells and then rounds up in region 3 to form a

follicle. By this stage, one cell has been se-

lected as the oocyte and the others become

nursecells(Fig.1A).Oocyteselectiondepends

on the formation of a noncentrosomal micro-

tubule organizing center (ncMTOC) in the

future oocyte that organizes a polarized mi-

crotubule (MT) network that directs the dynein-

dependent transport of cell fate determinants

and centrosomes into the pro-oocyte ( 6 – 8 )

(Fig. 1A). How symmetry is broken to specify

which cell contains the ncMTOC and becomes

theoocyteisunclear.

Patronin and its vertebrate orthologs (CAMSAPs)

are MT minus end-binding proteins that have

been recently found to be essential components

of ncMTOCs ( 9 – 13 ). To investigate the role of

Patronin in oocyte determination, we exam-

ined the distribution of oocyte markers in

patroninc9-c5mutant (MUT) cysts (Fig. 1, B

and C, and fig. S1). In wild-type (WT) cysts, Orb

and centrosomes accumulate in future oocytes

in regions 2b to 3 ( 14 – 16 )butarerarelylocal-

ized inpatroninmutants (24 and 3% of MUT

cysts, respectively) (Fig. 1, B and C). Several

germ cells enter meiosis in region 2a and ac-

cumulate the synaptonemal complex protein

C(3)G, which becomes restricted to two cells

in region 2b and to the oocyte in region 3 ( 17 )

(fig. S1). C(3)G is not localized in region 3 of

patronincysts, and 44% of the cysts in region

2b have three cells in meiosis (fig. S1). Thus,

Patronin is required for oocyte determination.

To determine whether Patronin is asym-

metrically distributed in the cyst, we imaged

germaria expressing endogenously tagged

Patronin-Kate. Patronin starts to accumulate

in a single cell in each cyst in region 2a, earlier

than other markers for the presumptive oocyte,

874 12 NOVEMBER 2021•VOL 374 ISSUE 6569 science.orgSCIENCE

(^1) The Gurdon Institute and the Department of Genetics,
University of Cambridge, Cambridge CB2 1QN, UK.^2 The
Department of Physiology, Development and Neuroscience,
University of Cambridge, Cambridge CB2 3DY, UK.
*Corresponding author. Email: [email protected]
(D.S.J.); [email protected] (D.N.)
†Present address: Institute for Cell and Molecular Biosciences,
Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
RESEARCH