Ownership Submission
FORM 4
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
KANIA EDWIN M JR
   2. Issuer Name and Ticker or Trading Symbol
ACCELERON PHARMA INC [XLRN] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
__X__ Director _____ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
(Last)
(First)
(Middle)
C/O FLAGSHIP VENTURES, 1 MEMORIAL DRIVE		 3. Date of Earliest Transaction (Month/Day/Year)
12/23/2014
(Street)

CAMBRIDGE, MA 02142		 4. If Amendment, Date Original Filed(Month/Day/Year)
 6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)		 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code
(Instr. 8)		 4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)		 5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4)		 6. Ownership Form: Direct (D) or Indirect (I)
(Instr. 4)		 7. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V Amount (A) or (D) Price
Common Stock 12/23/2014   S   51,163 D $ 38 (1) 0 I See Footnote (2)
Common Stock 12/23/2014   S   3,187 D $ 38 (1) 0 I See Footnote (3)
Common Stock               500,420 I See Footnote (4)
Common Stock               30,248 I See Footnote (5)
Common Stock               13,136 I See Footnote (6)
Common Stock               251 I See Footnote (7)
Common Stock               28,734 D  

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 3)		 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code
(Instr. 8)		 5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4, and 5)		 6. Date Exercisable and Expiration Date
(Month/Day/Year)		 7. Title and Amount of Underlying Securities
(Instr. 3 and 4)		 8. Price of Derivative Security
(Instr. 5)		 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 4)		 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 4)		 11. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
KANIA EDWIN M JR
C/O FLAGSHIP VENTURES, 1 MEMORIAL DRIVE
CAMBRIDGE, MA 02142		   X      

Signatures

 /s/Edwin M. Kania, Jr.   12/24/2014
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) The price reported in Column 4 is a weighted average price. These shares were disposed of by OneLiberty Ventures 2000, L.P. ("OLV") and OneLiberty Advisors Fund 2000, L.P. ("OLA") in multiple transactions on the Transaction Date at prices ranging from $37.99 to $38.05, inclusive. The reporting person undertakes to provide to Acceleron Pharma Inc., any security holder of Acceleron Pharma Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the foregoing price range.
(2) These shares were held directly by OLV. OneLiberty Partners 2000, LLC ("OLP") is the general partner of OLV. Edwin M. Kania, Jr. is the managing member of OLP and, accordingly, may be deemed to have beneficial ownership with respect to all shares held by OLV. Mr. Kania disclaims beneficial ownership of such shares, except to the extent of his pecuniary interest therein.
(3) These shares were held directly by OLA. OLP is the general partner of OLA. As managing member of OLP, Edwin M. Kania, Jr. may be deemed to have beneficial ownership with respect to all shares held by OLA. Mr. Kania disclaims beneficial ownership of such shares, except to the extent of his pecuniary interest therein.
(4) These shares are held directly by Applied Genomic Technology Capital Fund, L.P. ("AGTC Fund"). NewcoGen Group, Inc. ("NewcoGen Inc.") is the sole general partner of AGTC Partners, L.P. ("AGTC Partners"), which is the sole general partner of AGTC Fund. NewcoGen Inc. is a wholly-owned subsidiary of Flagship Ventures Management, Inc. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. are the directors of Flagship Ventures Management, Inc. and, accordingly, may be deemed to have beneficial ownership with respect to all shares held by AGTC Fund. Each of Mr. Kania and Dr. Afeyan disclaims beneficial ownership of such shares, except to the extent of his pecuniary interest therein.
(5) These shares are held directly by AGTC Advisors Fund, L.P ("AGTC Advisors"). NewcoGen Inc. is the sole general partner of AGTC Partners, which is the sole general partner of AGTC Advisors. NewcoGen Inc. is a wholly-owned subsidiary of Flagship Ventures Management, Inc. As the directors of Flagship Ventures Management, Inc., Noubar B. Afeyan Ph.D. and Edwin M. Kania, Jr. may be deemed to have beneficial ownership with respect to all shares held by AGTC Advisors. Each of Mr. Kania and Dr. Afeyan disclaims beneficial ownership of such shares, except to the extent of his pecuniary interest therein.
(6) These shares are held by NewcoGen Group LLC. NewcoGen Inc. is the manager of NewcoGen Group LLC and is a wholly-owned subsidiary of Flagship Ventures Management, Inc. As the directors of Flagship Ventures Management, Inc., Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. may be deemed to have beneficial ownership with respect to all shares held by NewcoGen Group LLC. Each of Mr. Kania and Dr. Afeyan disclaims beneficial ownership of such shares, except to the extent of his pecuniary interest therein.
(7) These shares are held directly by AGTC Partners. NewcoGen Inc. is the general partner of AGTC Partners. NewcoGen Inc. is a wholly-owned subsidiary of Flagship Ventures Management, Inc. As the directors of Flagship Ventures Management, Inc., Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. may be deemed to have beneficial ownership with respect to all shares held by AGTC Partners. Each of Mr. Kania and Dr. Afeyan disclaims beneficial ownership of such shares, except to the extent of his pecuniary interest therein.

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